Deep cloning objects

Question

I want to do something like   MyObject myObj   GetMyObj       Create and fill a new object MyObject newObj   myObj Clone      And then make changes to the new object that are not reflected in the original object   I don t often need this functionality  so when it s been necessary  I ve resorted to creating a new object and then copying each property individually  but it always leaves me with the feeling that there is a better or more elegant way of handling the situation   How can I clone or deep copy an object so that the cloned object can be modified without any changes being reflected in the original object

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Follow these steps    Define an ISelf lt T gt  with a read-only Self property that returns T  and ICloneable lt out T gt   which derives from ISelf lt T gt  and includes a method T Clone    Then define a CloneBase type which implements a protected virtual generic VirtualClone casting MemberwiseClone to the passed-in type    Each derived type should implement VirtualClone by calling the base clone method and then doing whatever needs to be done to properly clone those aspects of the derived type which the parent VirtualClone method hasn t yet handled    For maximum inheritance versatility  classes exposing public cloning functionality should be sealed  but derive from a base class which is otherwise identical except for the lack of cloning   Rather than passing variables of the explicit clonable type  take a parameter of type ICloneable lt theNonCloneableType gt    This will allow a routine that expects a cloneable derivative of  Foo to work with a cloneable derivative of DerivedFoo  but also allow the creation of non-cloneable derivatives of Foo

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I know that this question and answer sits here for a while and following is not quite answer but rather observation  to which I came across recently when I was checking whether indeed privates are not being cloned  I wouldn t be myself if I have not    when I happily copy-pasted  johnc updated answer   I simply made myself extension method  which is pretty much copy-pasted form aforementioned answer    public static class CloneThroughJsonExtension       private static readonly JsonSerializerSettings DeserializeSettings   new JsonSerializerSettings   ObjectCreationHandling   ObjectCreationHandling Replace         public static T CloneThroughJson lt T gt  this T source                return ReferenceEquals source  null    default T    JsonConvert DeserializeObject lt T gt  JsonConvert SerializeObject source   DeserializeSettings             and dropped naively class like this  in fact there was more of those but they are unrelated    public class WhatTheHeck       public string PrivateSet   get  private set       matches ctor param name      public string GetOnly   get       matches ctor param name      private readonly string  indirectField      public string Indirect   gt    Inception of    indirectField        matches ctor param name     public string RealIndirectFieldVaule   gt   indirectField       public WhatTheHeck string privateSet  string getOnly  string indirect                PrivateSet   privateSet          GetOnly   getOnly           indirectField   indirect            and code like this   var clone   new WhatTheHeck  Private-Set-Prop cloned     Get-Only-Prop cloned     Indirect-Field clonned    CloneThroughJson    Console WriteLine   1   clone PrivateSet     Console WriteLine   2   clone GetOnly     Console WriteLine   3 1   clone Indirect     Console WriteLine   3 2   clone RealIndirectFieldVaule       resulted in   1  Private-Set-Prop cloned  2  Get-Only-Prop cloned  3 1  Inception of  Inception of  Indirect-Field cloned  3 2  Inception of  Indirect-Field cloned    I was whole like  WHAT THE F    so I grabbed Newtonsoft Json Github repo and started to dig  What it comes out  is that  while deserializing a type which happens to have only one ctor and its param names match  case insensitive  public property names they will be passed to ctor as those params  Some clues can be found in the code here and here   Bottom line  I know that it is rather not common case and example code is bit abusive  but hey  It got me by surprise when I was checking whether there is any dragon waiting in the bushes to jump out and bite me in the ass

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The short answer is you inherit from the ICloneable interface and then implement the  clone function  Clone should do a memberwise copy and perform a deep copy on any member that requires it  then return the resulting object  This is a recursive operation   it requires that all members of the class you want to clone are either value types or implement ICloneable and that their members are either value types or implement ICloneable  and so on    For a more detailed explanation on Cloning using ICloneable  check out this article   The long answer is  it depends   As mentioned by others  ICloneable is not supported by generics  requires special considerations for circular class references  and is actually viewed by some as a  mistake  in the  NET Framework  The serialization method depends on your objects being serializable  which they may not be and you may have no control over  There is still much debate in the community over which is the  best  practice  In reality  none of the solutions are the one-size fits all best practice for all situations like ICloneable was originally interpreted to be   See the this Developer s Corner article for a few more options  credit to Ian

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The generic approaches are all technically valid  but I just wanted to add a note from myself since we rarely actually need a real deep copy  and I would strongly oppose using generic deep copying in actual business applications since that makes it so you might have many places where the objects are copied and then modified explicitly  its easy to get lost    In most real-life situations also you want to have as much granular control over the copying process as possible since you are not only coupled to the data access framework but also in practice the copied business objects should rarely be 100  the same  Think an example  referenceId s used by the ORM to identify object references  a full deep copy will also copy this id s so while in-memory the objects will be different  as soon as you submit it to the datastore  it will complain  so you will have to modify this properties manually after copying anyway and if the object changes you need to adjust it in all of the places which use the generic deep copying   Expanding on  cregox answer with ICloneable  what actually is a deep copy  Its just a newly allocated object on the heap that is identical to the original object but occupies a different memory space  as such rather than using a generic cloner functionality why not just create a new object   I personally use the idea of static factory methods on my domain objects   Example       public class Client               public string Name   get  set             protected Client                                public static Client Clone Client copiedClient                        return new Client                               Name   copiedClient Name                                     public class Shop               public string Name   get  set             public string Address   get  set             public ICollection lt Client gt  Clients   get  set             public static Shop Clone Shop copiedShop  string newAddress  ICollection lt Client gt  clients                        var copiedClients   new List lt Client gt                 foreach  var client in copiedShop Clients                                copiedClients Add Client Clone client                               return new Shop                               Name   copiedShop Name                  Address   newAddress                  Clients   copiedClients                                  If someone is looking how he can structure object instantiation while retaining full control over the copying process that s a solution that I have been personally very successful with  The protected constructors also make it so  other developers are forced to use the factory methods which gives a neat single point of object instantiation encapsulating the construction logic inside of the object  You can also overload the method and have several clone logic s for different places if necessary

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If you re already using a 3rd party application like ValueInjecter or Automapper  you can do something like this   MyObject oldObj     The existing object to clone  MyObject newObj   new MyObject    newObj InjectFrom oldObj      Using ValueInjecter syntax   Using this method you don t have to implement ISerializable or ICloneable on your objects  This is common with the MVC MVVM pattern  so simple tools like this have been created   see the ValueInjecter deep cloning sample on GitHub

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The reason not to use ICloneable is not because it doesn t have a generic interface   The reason not to use it is because it s vague   It doesn t make clear whether you re getting a shallow or a deep copy  that s up to the implementer   Yes  MemberwiseClone makes a shallow copy  but the opposite of MemberwiseClone isn t Clone  it would be  perhaps  DeepClone  which doesn t exist   When you use an object through its ICloneable interface  you can t know which kind of cloning the underlying object performs    And XML comments won t make it clear  because you ll get the interface comments rather than the ones on the object s Clone method    What I usually do is simply make a Copy method that does exactly what I want

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DeepCloner  Quick  easy  effective NuGet package to solve cloning  After reading all answers I was surprised no one mentioned this excellent package    DeepCloner GitHub project    DeepCloner NuGet package  Elaborating a bit on its README  here are the reason why we chose it at work         It can deep or shallow copy    In deep cloning all object graph is maintained     Uses code-generation in runtime  as result cloning is blazingly fast   Objects copied by internal structure  no methods or ctors called   You don t need to mark classes somehow  like Serializable-attribute  or implement interfaces    No requirement to specify object type for cloning  Object can be casted to interface or as an abstract object  e g  you can clone array of ints as abstract Array or IEnumerable  even null can be cloned without any errors    Cloned object doesn t have any ability to determine that he is clone  except with very specific methods       Usage   var deepClone   new   Id   1  Name    222    DeepClone    var shallowClone   new   Id   1  Name    222    ShallowClone      Performance   The README contains a performance comparison of various cloning libraries and methods  DeepCloner Performance   Requirements     NET 4 0 or higher or  NET Standard 1 3   NET Core  Requires Full Trust permission set or Reflection permission  MemberAccess

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Using System Text Json   https   devblogs microsoft com dotnet try-the-new-system-text-json-apis   public static T DeepCopy lt T gt  this T source        return source    null   default   JsonSerializer Parse lt T gt  JsonSerializer ToString source        The new API is using Span lt T gt   This should be fast  would be nice to do some benchmarks   Note  there s no need for ObjectCreationHandling Replace like in Json NET as it will replace collection values by default  You should forget about Json NET now as everything is going to be replaced with the new official API   I m not sure this will work with private fields

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I wanted a cloner for very simple objects of mostly primitives and lists   If your object is out of the box JSON serializable then this method will do the trick   This requires no modification or implementation of interfaces on the cloned class  just a JSON serializer like JSON NET   public static T Clone lt T gt  T source        var serialized   JsonConvert SerializeObject source       return JsonConvert DeserializeObject lt T gt  serialized       Also  you can use this extension method  public static class SystemExtension       public static T Clone lt T gt  this T source                var serialized   JsonConvert SerializeObject source           return JsonConvert DeserializeObject lt T gt  serialized

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I have created a version of the accepted answer that works with both   Serializable   and   DataContract    It has been a while since I wrote it  but if I remember correctly  DataContract  needed a different serializer   Requires System  System IO  System Runtime Serialization  System Runtime Serialization Formatters Binary  System Xml   public static class ObjectCopier             lt summary gt          Perform a deep Copy of an object that is marked with   Serializable   or   DataContract            lt  summary gt           lt typeparam name  T  gt The type of object being copied  lt  typeparam gt           lt param name  source  gt The object instance to copy  lt  param gt           lt returns gt The copied object  lt  returns gt      public static T Clone lt T gt  T source                if  typeof T  IsSerializable    true                        return CloneUsingSerializable lt T gt  source                      if  IsDataContract typeof T      true                        return CloneUsingDataContracts lt T gt  source                      throw new ArgumentException  The type must be Serializable or use DataContracts     source                     lt summary gt          Perform a deep Copy of an object that is marked with   Serializable            lt  summary gt           lt remarks gt          Found on http   stackoverflow com questions 78536 cloning-objects-in-c-sharp         Uses code found on CodeProject  which allows free use in third party apps         - http   www codeproject com KB tips SerializedObjectCloner aspx          lt  remarks gt           lt typeparam name  T  gt The type of object being copied  lt  typeparam gt           lt param name  source  gt The object instance to copy  lt  param gt           lt returns gt The copied object  lt  returns gt      public static T CloneUsingSerializable lt T gt  T source                if   typeof T  IsSerializable                        throw new ArgumentException  The type must be serializable     source                          Don t serialize a null object  simply return the default for that object         if  Object ReferenceEquals source  null                         return default T                      IFormatter formatter   new BinaryFormatter            Stream stream   new MemoryStream            using  stream                        formatter Serialize stream  source               stream Seek 0  SeekOrigin Begin               return  T formatter Deserialize stream                              lt summary gt          Perform a deep Copy of an object that is marked with   DataContract            lt  summary gt           lt typeparam name  T  gt The type of object being copied  lt  typeparam gt           lt param name  source  gt The object instance to copy  lt  param gt           lt returns gt The copied object  lt  returns gt      public static T CloneUsingDataContracts lt T gt  T source                if  IsDataContract typeof T      false                        throw new ArgumentException  The type must be a data contract     source                             Don t serialize a null object  simply return the default for that object         if  Object ReferenceEquals source  null                         return default T                      DataContractSerializer dcs   new DataContractSerializer typeof T            using Stream stream   new MemoryStream                          using  XmlDictionaryWriter writer   XmlDictionaryWriter CreateBinaryWriter stream                                 dcs WriteObject writer  source                   writer Flush                    stream Seek 0  SeekOrigin Begin                   using  XmlDictionaryReader reader   XmlDictionaryReader CreateBinaryReader stream  XmlDictionaryReaderQuotas Max                                         return  T dcs ReadObject reader                                                              lt summary gt          Helper function to check if a class is a  DataContract           lt  summary gt           lt param name  type  gt The type of the object to check  lt  param gt           lt returns gt Boolean flag indicating if the class is a DataContract  true  or not  false   lt  returns gt      public static bool IsDataContract Type type                object   attributes   type GetCustomAttributes typeof DataContractAttribute   false           return attributes Length    1

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Here a solution fast and easy that worked for me without relaying on Serialization Deserialization    public class MyClass       public virtual MyClass DeepClone                 var returnObj    MyClass MemberwiseClone            var type   returnObj GetType            var fieldInfoArray   type GetRuntimeFields   ToArray             foreach  var fieldInfo in fieldInfoArray                        object sourceFieldValue   fieldInfo GetValue this               if    sourceFieldValue is MyClass                                 continue                             var sourceObj    MyClass sourceFieldValue              var clonedObj   sourceObj DeepClone                fieldInfo SetValue returnObj  clonedObj                     return returnObj            EDIT  requires       using System Linq      using System Reflection    That s How I used it  public MyClass Clone MyClass theObjectIneededToClone        MyClass clonedObj   theObjectIneededToClone DeepClone

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The reason not to use ICloneable is not because it doesn t have a generic interface   The reason not to use it is because it s vague   It doesn t make clear whether you re getting a shallow or a deep copy  that s up to the implementer   Yes  MemberwiseClone makes a shallow copy  but the opposite of MemberwiseClone isn t Clone  it would be  perhaps  DeepClone  which doesn t exist   When you use an object through its ICloneable interface  you can t know which kind of cloning the underlying object performs    And XML comments won t make it clear  because you ll get the interface comments rather than the ones on the object s Clone method    What I usually do is simply make a Copy method that does exactly what I want

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I prefer a copy constructor to a clone  The intent is clearer

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I wanted a cloner for very simple objects of mostly primitives and lists   If your object is out of the box JSON serializable then this method will do the trick   This requires no modification or implementation of interfaces on the cloned class  just a JSON serializer like JSON NET   public static T Clone lt T gt  T source        var serialized   JsonConvert SerializeObject source       return JsonConvert DeserializeObject lt T gt  serialized       Also  you can use this extension method  public static class SystemExtension       public static T Clone lt T gt  this T source                var serialized   JsonConvert SerializeObject source           return JsonConvert DeserializeObject lt T gt  serialized

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Yet another JSON NET answer  This version works with classes that don t implement ISerializable   public static class Cloner       public static T Clone lt T gt  T source                if  ReferenceEquals source  null               return default T            var settings   new JsonSerializerSettings   ContractResolver   new ContractResolver               return JsonConvert DeserializeObject lt T gt  JsonConvert SerializeObject source  settings   settings              class ContractResolver   DefaultContractResolver               protected override IList lt JsonProperty gt  CreateProperties Type type  MemberSerialization memberSerialization                        var props   type GetProperties BindingFlags Public   BindingFlags NonPublic   BindingFlags Instance                   Select p   gt  base CreateProperty p  memberSerialization                    Union type GetFields BindingFlags Public   BindingFlags NonPublic   BindingFlags Instance                       Select f   gt  base CreateProperty f  memberSerialization                     ToList                props ForEach p   gt    p Writable   true  p Readable   true                  return props

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The reason not to use ICloneable is not because it doesn t have a generic interface   The reason not to use it is because it s vague   It doesn t make clear whether you re getting a shallow or a deep copy  that s up to the implementer   Yes  MemberwiseClone makes a shallow copy  but the opposite of MemberwiseClone isn t Clone  it would be  perhaps  DeepClone  which doesn t exist   When you use an object through its ICloneable interface  you can t know which kind of cloning the underlying object performs    And XML comments won t make it clear  because you ll get the interface comments rather than the ones on the object s Clone method    What I usually do is simply make a Copy method that does exactly what I want

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As I couldn t find a cloner that meets all my requirements in different projects  I created a deep cloner that can be configured and adapted to different code structures instead of adapting my code to meet the cloners requirements  Its achieved by adding annotations to the code that shall be cloned or you just leave the code as it is to have the default behaviour  It uses reflection  type caches and is based on fasterflect  The cloning process is very fast for a huge amount of data and a high object hierarchy  compared to other reflection serialization based algorithms     https   github com kalisohn CloneBehave  Also available as a nuget package  https   www nuget org packages Clone Behave 1 0 0  For example  The following code will deepClone Address  but only perform a shallow copy of the  currentJob field    public class Person       DeepClone DeepCloneBehavior Shallow     private Job  currentJob           public string Name   get  set       public Job CurrentJob           get  return  currentJob        set   currentJob   value           public Person Manager   get  set       public class Address            public Person PersonLivingHere   get  set       Address adr   new Address    adr PersonLivingHere   new Person  John    adr PersonLivingHere BestFriend   new Person  James    adr PersonLivingHere CurrentJob   new Job  Programmer     Address adrClone   adr Clone       RESULT adr PersonLivingHere    adrClone PersonLivingHere   false adr PersonLivingHere Manager    adrClone PersonLivingHere Manager   false adr PersonLivingHere CurrentJob    adrClone PersonLivingHere CurrentJob   true adr PersonLivingHere CurrentJob AnyProperty    adrClone PersonLivingHere CurrentJob AnyProperty   true

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Create an extension  public static T Clone lt T gt  this T theObject        string jsonData   JsonConvert SerializeObject theObject       return JsonConvert DeserializeObject lt T gt  jsonData      And call it like this  NewObject   OldObject Clone

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After much much reading about many of the options linked here  and possible solutions for this issue  I believe all the options are summarized pretty well at Ian P s link  all other options are variations of those  and the best solution is provided by Pedro77 s link on the question comments   So I ll just copy relevant parts of those 2 references here  That way we can have   The best thing to do for cloning objects in C sharp   First and foremost  those are all our options    Manually with ICloneable  which is Shallow and not Type-Safe MemberwiseClone  which uses ICloneable Reflection by using Activator CreateInstance and recursive MemberwiseClone Serialization  as pointed by johnc s preferred answer Intermediate Language  which I got no idea how works Extension Methods  such as this custom clone framework by Havard Straden Expression Trees   The article Fast Deep Copy by Expression Trees   has  also performance comparison of cloning by Serialization  Reflection and Expression Trees   Why I choose ICloneable  i e  manually   Mr Venkat Subramaniam  redundant link here  explains in much detail why   All his article circles around an example that tries to be applicable for most cases  using 3 objects  Person  Brain and City  We want to clone a person  which will have its own brain but the same city  You can either picture all problems any of the other methods above can bring or read the article   This is my slightly modified version of his conclusion      Copying an object by specifying New followed by the class name often leads to code that is not extensible  Using clone  the application of prototype pattern  is a better way to achieve this  However  using clone as it is provided in C   and Java  can be quite problematic as well  It is better to provide a protected  non-public  copy constructor and invoke that from the clone method  This gives us the ability to delegate the task of creating an object to an instance of a class itself  thus providing extensibility and also  safely creating the objects using the protected copy constructor    Hopefully this implementation can make things clear   public class Person   ICloneable       private final Brain brain     brain is final since I do not want                     any transplant on it once created      private int age      public Person Brain aBrain  int theAge                brain   aBrain           age   theAge            protected Person Person another                Brain refBrain   null          try                       refBrain    Brain  another brain clone                   You can set the brain in the constructor                   catch CloneNotSupportedException e             brain   refBrain          age   another age            public String toString                 return  This is person with     brain             Not meant to sound rude as it reads            public Object clone                 return new Person this                     Now consider having a class derive from Person   public class SkilledPerson extends Person       private String theSkills      public SkilledPerson Brain aBrain  int theAge  String skills                super aBrain  theAge           theSkills   skills            protected SkilledPerson SkilledPerson another                super another           theSkills   another theSkills             public Object clone                 return new SkilledPerson this             public String toString                 return  SkilledPerson      super toString              You may try running the following code   public class User       public static void play Person p                Person another    Person  p clone            System out println p           System out println another             public static void main String   args                Person sam   new Person new Brain    1           play sam           SkilledPerson bob   new SkilledPerson new SmarterBrain    1   Writer            play bob             The output produced will be   This is person with Brain 1fcc69 This is person with Brain 253498 SkilledPerson  This is person with SmarterBrain 1fef6f SkilledPerson  This is person with SmarterBrain 209f4e   Observe that  if we keep a count of the number of objects  the clone as implemented here will keep a correct count of the number of objects

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After much much reading about many of the options linked here  and possible solutions for this issue  I believe all the options are summarized pretty well at Ian P s link  all other options are variations of those  and the best solution is provided by Pedro77 s link on the question comments   So I ll just copy relevant parts of those 2 references here  That way we can have   The best thing to do for cloning objects in C sharp   First and foremost  those are all our options    Manually with ICloneable  which is Shallow and not Type-Safe MemberwiseClone  which uses ICloneable Reflection by using Activator CreateInstance and recursive MemberwiseClone Serialization  as pointed by johnc s preferred answer Intermediate Language  which I got no idea how works Extension Methods  such as this custom clone framework by Havard Straden Expression Trees   The article Fast Deep Copy by Expression Trees   has  also performance comparison of cloning by Serialization  Reflection and Expression Trees   Why I choose ICloneable  i e  manually   Mr Venkat Subramaniam  redundant link here  explains in much detail why   All his article circles around an example that tries to be applicable for most cases  using 3 objects  Person  Brain and City  We want to clone a person  which will have its own brain but the same city  You can either picture all problems any of the other methods above can bring or read the article   This is my slightly modified version of his conclusion      Copying an object by specifying New followed by the class name often leads to code that is not extensible  Using clone  the application of prototype pattern  is a better way to achieve this  However  using clone as it is provided in C   and Java  can be quite problematic as well  It is better to provide a protected  non-public  copy constructor and invoke that from the clone method  This gives us the ability to delegate the task of creating an object to an instance of a class itself  thus providing extensibility and also  safely creating the objects using the protected copy constructor    Hopefully this implementation can make things clear   public class Person   ICloneable       private final Brain brain     brain is final since I do not want                     any transplant on it once created      private int age      public Person Brain aBrain  int theAge                brain   aBrain           age   theAge            protected Person Person another                Brain refBrain   null          try                       refBrain    Brain  another brain clone                   You can set the brain in the constructor                   catch CloneNotSupportedException e             brain   refBrain          age   another age            public String toString                 return  This is person with     brain             Not meant to sound rude as it reads            public Object clone                 return new Person this                     Now consider having a class derive from Person   public class SkilledPerson extends Person       private String theSkills      public SkilledPerson Brain aBrain  int theAge  String skills                super aBrain  theAge           theSkills   skills            protected SkilledPerson SkilledPerson another                super another           theSkills   another theSkills             public Object clone                 return new SkilledPerson this             public String toString                 return  SkilledPerson      super toString              You may try running the following code   public class User       public static void play Person p                Person another    Person  p clone            System out println p           System out println another             public static void main String   args                Person sam   new Person new Brain    1           play sam           SkilledPerson bob   new SkilledPerson new SmarterBrain    1   Writer            play bob             The output produced will be   This is person with Brain 1fcc69 This is person with Brain 253498 SkilledPerson  This is person with SmarterBrain 1fef6f SkilledPerson  This is person with SmarterBrain 209f4e   Observe that  if we keep a count of the number of objects  the clone as implemented here will keep a correct count of the number of objects

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Code Generator  We have seen a lot of ideas from serialization over manual implementation to reflection and I want to propose a totally different approach using the CGbR Code Generator  The generate clone method is memory and CPU efficient and therefor 300x faster as the standard DataContractSerializer   All you need is a partial class definition with ICloneable and the generator does the rest   public partial class Root   ICloneable       public Root int number                 number   number            private int  number       public Partial   Partials   get  set         public IList lt ulong gt  Numbers   get  set         public object Clone                 return Clone true              private Root                   public partial class Root       public Root Clone bool deep                var copy   new Root               All value types can be simply copied         copy  number    number           if  deep                           In a deep clone the references are cloned              var tempPartials   new Partial Partials Length               for  var i   0  i  lt  Partials Length  i                                  var value   Partials i                   value   value Clone true                   tempPartials i    value                            copy Partials   tempPartials              var tempNumbers   new List lt ulong gt  Numbers Count               for  var i   0  i  lt  Numbers Count  i                                  var value   Numbers i                   tempNumbers Add value                             copy Numbers   tempNumbers                    else                          In a shallow clone only references are copied             copy Partials   Partials               copy Numbers   Numbers                     return copy            Note  Latest version has a more null checks  but I left them out for better understanding

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This will copy all readable and writable properties of an object to another    public class PropertyCopy lt TSource  TTarget gt                           where TSource  class  new                           where TTarget  class  new                         public static TTarget Copy TSource src  TTarget trg  params string   properties                                if  src  null  return trg                  if  trg    null  trg   new TTarget                    var fulllist   src GetType   GetProperties   Where c   gt  c CanWrite  amp  amp  c CanRead  ToList                    if  properties    null  amp  amp  properties Count    gt  0                      fulllist   fulllist Where c   gt  properties Contains c Name   ToList                    if  fulllist    null    fulllist Count      0  return trg                   fulllist ForEach c   gt                                                c SetValue trg  c GetValue src                                             return trg                            and this is how you use it     var cloned   Utils PropertyCopy lt TKTicket  TKTicket gt  Copy  tmp  dbsave                                                               Creation                                                                Description                                                                IdTicketStatus                                                                IdUserCreated                                                                IdUserInCharge                                                                IdUserRequested                                                                IsUniqueTicketGenerated                                                                LastEdit                                                                Subject                                                                UniqeTicketRequestId                                                                Visibility      or to copy everything    var cloned   Utils PropertyCopy lt TKTicket  TKTicket gt  Copy  tmp  dbsave

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DeepCloner  Quick  easy  effective NuGet package to solve cloning  After reading all answers I was surprised no one mentioned this excellent package    DeepCloner GitHub project    DeepCloner NuGet package  Elaborating a bit on its README  here are the reason why we chose it at work         It can deep or shallow copy    In deep cloning all object graph is maintained     Uses code-generation in runtime  as result cloning is blazingly fast   Objects copied by internal structure  no methods or ctors called   You don t need to mark classes somehow  like Serializable-attribute  or implement interfaces    No requirement to specify object type for cloning  Object can be casted to interface or as an abstract object  e g  you can clone array of ints as abstract Array or IEnumerable  even null can be cloned without any errors    Cloned object doesn t have any ability to determine that he is clone  except with very specific methods       Usage   var deepClone   new   Id   1  Name    222    DeepClone    var shallowClone   new   Id   1  Name    222    ShallowClone      Performance   The README contains a performance comparison of various cloning libraries and methods  DeepCloner Performance   Requirements     NET 4 0 or higher or  NET Standard 1 3   NET Core  Requires Full Trust permission set or Reflection permission  MemberAccess

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I ve just created CloneExtensions library project  It performs fast  deep clone using simple assignment operations generated by Expression Tree runtime code compilation   How to use it   Instead of writing your own Clone or Copy methods with a tone of assignments between fields and properties make the program do it for yourself  using Expression Tree  GetClone lt T gt    method marked as extension method allows you to simply call it on your instance   var newInstance   source GetClone      You can choose what should be copied from source to newInstance using CloningFlags enum   var newInstance        source GetClone CloningFlags Properties   CloningFlags CollectionItems     What can be cloned    Primitive  int  uint  byte  double  char  etc    known immutable types  DateTime  TimeSpan  String  and delegates  including Action  Func  etc  Nullable T   arrays Custom classes and structs  including generic classes and structs    Following class struct members are cloned internally    Values of public  not readonly fields Values of public properties with both get and set accessors Collection items for types implementing ICollection   How fast it is   The solution is faster then reflection  because members information has to be gathered only once  before GetClone lt T gt  is used for the first time for given type T   It s also faster than serialization-based solution when you clone more then couple instances of the same type T   and more     Read more about generated expressions on documentation   Sample expression debug listing for List lt int gt     Lambda  Lambda1 lt System Func 4 System Collections Generic List 1 System Int32  CloneExtensions CloningFlags System Collections Generic IDictionary 2 System Type System Func 2 System Object System Object   System Collections Generic List 1 System Int32   gt       System Collections Generic List 1 System Int32   source      CloneExtensions CloningFlags  flags      System Collections Generic IDictionary 2 System Type System Func 2 System Object System Object    initializers         Block System Collections Generic List 1 System Int32   target             If   source    null                 Return  Label1   null              Else                Default System Void                      If                Call  initializers ContainsKey  Constant lt System Type gt  System Collections Generic List 1 System Int32                             target    System Collections Generic List 1 System Int32   Call   initializers Item  Constant lt System Type gt  System Collections Generic List 1 System Int32                  Invoke  System Object  source             Else                target    New System Collections Generic List 1 System Int32                        If                 System Byte  flags  amp   System Byte  Constant lt CloneExtensions CloningFlags gt  Fields       System Byte  Constant lt CloneExtensions CloningFlags gt  Fields                           Default System Void             Else                Default System Void                      If                 System Byte  flags  amp   System Byte  Constant lt CloneExtensions CloningFlags gt  Properties       System Byte  Constant lt CloneExtensions CloningFlags gt  Properties                           Block                      target Capacity    Call CloneExtensions CloneFactory GetClone                       source Capacity                       flags                       initializers                           Else                Default System Void                      If                 System Byte  flags  amp   System Byte  Constant lt CloneExtensions CloningFlags gt  CollectionItems       System Byte  Constant lt CloneExtensions CloningFlags gt  CollectionItems                           Block                  System Collections Generic IEnumerator 1 System Int32   var1                  System Collections Generic ICollection 1 System Int32   var2                     var1    System Collections Generic IEnumerator 1 System Int32   Call  source GetEnumerator                     var2    System Collections Generic ICollection 1 System Int32   target                   Loop                         If   Call  var1 MoveNext      False                             Call  var2 Add  Call CloneExtensions CloneFactory GetClone                                   var1 Current                                   flags                              initializers                      Else                        Break  Label2                                                  LabelTarget  Label2                   Else            Default System Void              Label          target      LabelTarget  Label1         what has the same meaning like following c  code    source  flags  initializers    gt        if source    null          return null       if initializers ContainsKey typeof List lt int gt            target    List lt int gt  initializers typeof List lt int gt    Invoke  object source       else         target   new List lt int gt          if  flags  amp  CloningFlags Properties     CloningFlags Properties                target Capacity   target Capacity GetClone flags  initializers              if  flags  amp  CloningFlags CollectionItems     CloningFlags CollectionItems                var targetCollection    ICollection lt int gt  target          foreach var item in  ICollection lt int gt  source                        targetCollection Add item Clone flags  initializers                         return target      Isn t it quite like how you d write your own Clone method for List lt int gt

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I ve seen it implemented through reflection as well  Basically there was a method that would iterate through the members of an object and appropriately copy them to the new object  When it reached reference types or collections I think it did a recursive call on itself  Reflection is expensive  but it worked pretty well

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It s unbelievable how much effort you can spend with IClonable interface - especially if you have heavy class hierarchies  Also MemberwiseClone works somehow oddly - it does not exactly clone even normal List type kind of structures   And of course most interesting dilemma for serialization is to serialize back references - e g  class hierarchies where you have child-parent relationships  I doubt that binary serializer will be able to help you in this case   It will end up with recursive loops   stack overflow    I somehow liked solution proposed here  How do you do a deep copy of an object in  NET  C  specifically    however - it did not support Lists  added that support  also took into account re-parenting   For parenting only rule which I have made that field or property should be named  parent   then it will be ignored by DeepClone  You might want to decide your own rules for back-references - for tree hierarchies it might be  left right   etc     Here is whole code snippet including test code    using System  using System Collections  using System Collections Generic  using System Diagnostics  using System Linq  using System Reflection  using System Text   namespace TestDeepClone       class Program               static void Main string   args                        A a   new A                a name    main A               a b list Add new B a    name    b1                  a b list Add new B a    name    b2                   A a2    A a DeepClone                a2 name    second A                   Perform re-parenting manually after deep copy              foreach  var b in a2 b list                   b parent   a2                Debug WriteLine  ok                          public class A               public String name    one           public List lt String gt  list   new List lt string gt             public List lt String gt  null list          public List lt B gt  b list   new List lt B gt             private int private pleaseCopyMeAsWell   5           public override string ToString                         return  A     name                             public class B               public B               public B A  parent    parent    parent            public A parent          public String name    two               public static class ReflectionEx               public static Type GetUnderlyingType this MemberInfo member                        Type type              switch  member MemberType                                case MemberTypes Field                      type     FieldInfo member  FieldType                      break                  case MemberTypes Property                      type     PropertyInfo member  PropertyType                      break                  case MemberTypes Event                      type     EventInfo member  EventHandlerType                      break                  default                      throw new ArgumentException  member must be if type FieldInfo  PropertyInfo or EventInfo    member                              return Nullable GetUnderlyingType type     type                          lt summary gt              Gets fields and properties into one array              Order of properties   fields will be preserved in order of appearance in class   struct   MetadataToken is used for sorting such cases               lt  summary gt               lt param name  type  gt Type from which to get lt  param gt               lt returns gt array of fields and properties lt  returns gt          public static MemberInfo   GetFieldsAndProperties this Type type                        List lt MemberInfo gt  fps   new List lt MemberInfo gt                 fps AddRange type GetFields                 fps AddRange type GetProperties                 fps   fps OrderBy x   gt  x MetadataToken  ToList                return fps ToArray                       public static object GetValue this MemberInfo member  object target                        if  member is PropertyInfo                                return  member as PropertyInfo  GetValue target  null                             else if  member is FieldInfo                                return  member as FieldInfo  GetValue target                             else                               throw new Exception  member must be either PropertyInfo or FieldInfo                                     public static void SetValue this MemberInfo member  object target  object value                        if  member is PropertyInfo                                 member as PropertyInfo  SetValue target  value  null                             else if  member is FieldInfo                                 member as FieldInfo  SetValue target  value                             else                               throw new Exception  destinationMember must be either PropertyInfo or FieldInfo                                          lt summary gt              Deep clones specific object              Analogue can be found here  https   stackoverflow com questions 129389 how-do-you-do-a-deep-copy-an-object-in-net-c-specifically             This is now improved version  list support added               lt  summary gt               lt param name  obj  gt object to be cloned lt  param gt               lt returns gt full copy of object  lt  returns gt          public static object DeepClone this object obj                        if  obj    null                  return null               Type type   obj GetType                 if  obj is IList                                IList list     IList obj                   IList newlist    IList Activator CreateInstance obj GetType    list Count                    foreach  object elem in list                      newlist Add DeepClone elem                     return newlist                  if              if  type IsValueType    type    typeof string                                 return obj                            else if  type IsArray                                Type elementType   Type GetType type FullName Replace       string Empty                    var array   obj as Array                  Array copied   Array CreateInstance elementType  array Length                    for  int i   0  i  lt  array Length  i                        copied SetValue DeepClone array GetValue i    i                    return Convert ChangeType copied  obj GetType                               else if  type IsClass                                object toret   Activator CreateInstance obj GetType                      MemberInfo   fields   type GetFieldsAndProperties                    foreach  MemberInfo field in fields                                           Don t clone parent back-reference classes   Using special kind of naming  parent                          to indicate child s parent class                      if  field Name     parent                                                 continue                                             object fieldValue   field GetValue obj                        if  fieldValue    null                          continue                       field SetValue toret  DeepClone fieldValue                                       return toret                            else                                  Don t know that type  don t know how to clone it                  if  Debugger IsAttached                      Debugger Break                     return null                            DeepClone

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Keep things simple and use AutoMapper as others mentioned  it s a simple little library to map one object to another    To copy an object to another with the same type  all you need is three lines of code   MyType source   new MyType    Mapper CreateMap lt MyType  MyType gt     MyType target   Mapper Map lt MyType  MyType gt  source     The target object is now a copy of the source object  Not simple enough  Create an extension method to use everywhere in your solution   public static T Copy lt T gt  this T source        T copy   default T       Mapper CreateMap lt T  T gt         copy   Mapper Map lt T  T gt  source       return copy      The extension method can be used as follow   MyType copy   source Copy

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In general  you implement the ICloneable interface and implement Clone yourself  C  objects have a built-in MemberwiseClone method that performs a shallow copy that can help you out for all the primitives   For a deep copy  there is no way it can know how to automatically do it

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This will copy all readable and writable properties of an object to another    public class PropertyCopy lt TSource  TTarget gt                           where TSource  class  new                           where TTarget  class  new                         public static TTarget Copy TSource src  TTarget trg  params string   properties                                if  src  null  return trg                  if  trg    null  trg   new TTarget                    var fulllist   src GetType   GetProperties   Where c   gt  c CanWrite  amp  amp  c CanRead  ToList                    if  properties    null  amp  amp  properties Count    gt  0                      fulllist   fulllist Where c   gt  properties Contains c Name   ToList                    if  fulllist    null    fulllist Count      0  return trg                   fulllist ForEach c   gt                                                c SetValue trg  c GetValue src                                             return trg                            and this is how you use it     var cloned   Utils PropertyCopy lt TKTicket  TKTicket gt  Copy  tmp  dbsave                                                               Creation                                                                Description                                                                IdTicketStatus                                                                IdUserCreated                                                                IdUserInCharge                                                                IdUserRequested                                                                IsUniqueTicketGenerated                                                                LastEdit                                                                Subject                                                                UniqeTicketRequestId                                                                Visibility      or to copy everything    var cloned   Utils PropertyCopy lt TKTicket  TKTicket gt  Copy  tmp  dbsave

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In general  you implement the ICloneable interface and implement Clone yourself  C  objects have a built-in MemberwiseClone method that performs a shallow copy that can help you out for all the primitives   For a deep copy  there is no way it can know how to automatically do it

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Basically you need to implement ICloneable interface and then realize object structure copying   If it s deep copy of all members  you need to insure  not relating on solution you choose  that all children are clonable as well   Sometimes you need to be aware of some restriction during this process  for example if you copying the ORM objects most of frameworks allow only one object attached to the session and you MUST NOT make clones of this object  or if it s possible you need to care about session attaching of these objects    Cheers

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If your Object Tree is Serializeable you could also use something like this  static public MyClass Clone MyClass myClass        MyClass clone      XmlSerializer ser   new XmlSerializer typeof MyClass    xmlAttributeOverrides       using  var ms   new MemoryStream                  ser Serialize ms  myClass           ms Position   0          clone    MyClass ser Deserialize ms             return clone      be informed that this Solution is pretty easy but it s not as performant as other solutions may be   And be sure that if the Class grows  there will still be only those fields cloned  which also get serialized

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The short answer is you inherit from the ICloneable interface and then implement the  clone function  Clone should do a memberwise copy and perform a deep copy on any member that requires it  then return the resulting object  This is a recursive operation   it requires that all members of the class you want to clone are either value types or implement ICloneable and that their members are either value types or implement ICloneable  and so on    For a more detailed explanation on Cloning using ICloneable  check out this article   The long answer is  it depends   As mentioned by others  ICloneable is not supported by generics  requires special considerations for circular class references  and is actually viewed by some as a  mistake  in the  NET Framework  The serialization method depends on your objects being serializable  which they may not be and you may have no control over  There is still much debate in the community over which is the  best  practice  In reality  none of the solutions are the one-size fits all best practice for all situations like ICloneable was originally interpreted to be   See the this Developer s Corner article for a few more options  credit to Ian

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For the cloning process  the object can be converted to the byte array first and then converted back to the object   public static class Extentions       public static T Clone lt T gt  this T obj                byte   buffer   BinarySerialize obj           return  T BinaryDeserialize buffer              public static byte   BinarySerialize object obj                using  var stream   new MemoryStream                          var formatter   new BinaryFormatter                 formatter Serialize stream  obj                return stream ToArray                         public static object BinaryDeserialize byte   buffer                using  var stream   new MemoryStream buffer                        var formatter   new BinaryFormatter                return formatter Deserialize stream                       The object must be serialized for the serialization process    Serializable  public class MyObject       public string Name    get  set        Usage   MyObject myObj    GetMyObj    MyObject newObj   myObj Clone

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EDIT  project is discontinued  If you want true cloning to unknown types you can take a look at fastclone   That s expression based cloning working about 10 times faster than binary serialization and maintaining complete object graph integrity   That means  if you refer multiple times to the same object in your hierachy  the clone will also have a single instance beeing referenced   There is no need for interfaces  attributes or any other modification to the objects being cloned

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Code Generator  We have seen a lot of ideas from serialization over manual implementation to reflection and I want to propose a totally different approach using the CGbR Code Generator  The generate clone method is memory and CPU efficient and therefor 300x faster as the standard DataContractSerializer   All you need is a partial class definition with ICloneable and the generator does the rest   public partial class Root   ICloneable       public Root int number                 number   number            private int  number       public Partial   Partials   get  set         public IList lt ulong gt  Numbers   get  set         public object Clone                 return Clone true              private Root                   public partial class Root       public Root Clone bool deep                var copy   new Root               All value types can be simply copied         copy  number    number           if  deep                           In a deep clone the references are cloned              var tempPartials   new Partial Partials Length               for  var i   0  i  lt  Partials Length  i                                  var value   Partials i                   value   value Clone true                   tempPartials i    value                            copy Partials   tempPartials              var tempNumbers   new List lt ulong gt  Numbers Count               for  var i   0  i  lt  Numbers Count  i                                  var value   Numbers i                   tempNumbers Add value                             copy Numbers   tempNumbers                    else                          In a shallow clone only references are copied             copy Partials   Partials               copy Numbers   Numbers                     return copy            Note  Latest version has a more null checks  but I left them out for better understanding

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This method solved the problem for me   private static MyObj DeepCopy MyObj source                         var DeserializeSettings   new JsonSerializerSettings   ObjectCreationHandling   ObjectCreationHandling Replace                 return JsonConvert DeserializeObject lt MyObj  gt  JsonConvert SerializeObject source   DeserializeSettings                Use it like this  MyObj a   DeepCopy b

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I like Copyconstructors like that       public AnyObject AnyObject anyObject                foreach  var property in typeof AnyObject  GetProperties                          property SetValue this  property GetValue anyObject                      foreach  var field in typeof AnyObject  GetFields                          field SetValue this  field GetValue anyObject                      If you have more things to copy add them

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I think you can try this   MyObject myObj   GetMyObj       Create and fill a new object MyObject newObj   new MyObject myObj     DeepClone it

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I found a new way to do it that is Emit   We can use Emit to add the IL to app and run it  But I dont think its a good way for I want to perfect this that I write my answer   The Emit can see the official document and Guide  You should learn some IL to read the code  I will write the code that can copy the property in class   public static class Clone                  ReSharper disable once InconsistentNaming     public static void CloneObjectWithIL lt T gt  T source  T los                  see http   lindexi oschina io lindexi post C- E4 BD BF E7 94 A8Emit E6 B7 B1 E5 85 8B E9 9A 86          if  CachedIl ContainsKey typeof T                            Action lt T  T gt   CachedIl typeof T    source  los               return                    var dynamicMethod   new DynamicMethod  Clone   null  new     typeof T   typeof T              ILGenerator generator   dynamicMethod GetILGenerator             foreach  var temp in typeof T  GetProperties   Where temp   gt  temp CanRead  amp  amp  temp CanWrite                           do not copy static that will except             if  temp GetAccessors true  0  IsStatic                                continue                             generator Emit OpCodes Ldarg 1     los             generator Emit OpCodes Ldarg 0     s             generator Emit OpCodes Callvirt  temp GetMethod               generator Emit OpCodes Callvirt  temp SetMethod                     generator Emit OpCodes Ret           var clone    Action lt T  T gt   dynamicMethod CreateDelegate typeof Action lt T  T gt             CachedIl typeof T     clone          clone source  los              private static Dictionary lt Type  Delegate gt  CachedIl   set  get      new Dictionary lt Type  Delegate gt         The code can be deep copy but it can copy the property  If you want to make it to deep copy that you can change it for the IL is too hard that I cant do it

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In general  you implement the ICloneable interface and implement Clone yourself  C  objects have a built-in MemberwiseClone method that performs a shallow copy that can help you out for all the primitives   For a deep copy  there is no way it can know how to automatically do it

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Whereas one approach is to implement the ICloneable interface  described here  so I won t regurgitate   here s a nice deep clone object copier I found on The Code Project a while ago and incorporated it into our code  As mentioned elsewhere  it requires your objects to be serializable  using System  using System IO  using System Runtime Serialization  using System Runtime Serialization Formatters Binary        lt summary gt      Reference Article http   www codeproject com KB tips SerializedObjectCloner aspx     Provides a method for performing a deep copy of an object      Binary Serialization is used to perform the copy       lt  summary gt  public static class ObjectCopier            lt summary gt          Perform a deep copy of the object via serialization           lt  summary gt           lt typeparam name  quot T quot  gt The type of object being copied  lt  typeparam gt           lt param name  quot source quot  gt The object instance to copy  lt  param gt           lt returns gt A deep copy of the object  lt  returns gt      public static T Clone lt T gt  T source                if   typeof T  IsSerializable                        throw new ArgumentException  quot The type must be serializable  quot   nameof source                          Don t serialize a null object  simply return the default for that object         if  ReferenceEquals self  null   return default           using var Stream stream   new MemoryStream            IFormatter formatter   new BinaryFormatter            formatter Serialize stream  source           stream Seek 0  SeekOrigin Begin           return  T formatter Deserialize stream            The idea is that it serializes your object and then deserializes it into a fresh object  The benefit is that you don t have to concern yourself about cloning everything when an object gets too complex  In case of you prefer to use the new extension methods of C  3 0  change the method to have the following signature  public static T Clone lt T gt  this T source                 Now the method call simply becomes objectBeingCloned Clone     EDIT  January 10 2015  Thought I d revisit this  to mention I recently started using  Newtonsoft  Json to do this  it should be lighter  and avoids the overhead of  Serializable  tags   NB  atconway has pointed out in the comments that private members are not cloned using the JSON method       lt summary gt      Perform a deep Copy of the object  using Json as a serialization method  NOTE  Private members are not cloned using this method       lt  summary gt       lt typeparam name  quot T quot  gt The type of object being copied  lt  typeparam gt       lt param name  quot source quot  gt The object instance to copy  lt  param gt       lt returns gt The copied object  lt  returns gt  public static T CloneJson lt T gt  this T source                       Don t serialize a null object  simply return the default for that object     if  ReferenceEquals self  null   return default          initialize inner objects individually        for example in default constructor some list property initialized with some values         but in  source  these items are cleaned -        without ObjectCreationHandling Replace default constructor values will be added to result     var deserializeSettings   new JsonSerializerSettings  ObjectCreationHandling   ObjectCreationHandling Replace        return JsonConvert DeserializeObject lt T gt  JsonConvert SerializeObject source   deserializeSettings

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When using Marc Gravells protobuf-net as your serializer the accepted answer needs some slight modifications  as the object to copy won t be attributed with  Serializable  and  therefore  isn t serializable and the Clone-method will throw an exception  I modified it to work with protobuf-net   public static T Clone lt T gt  this T source        if Attribute GetCustomAttribute typeof T   typeof ProtoBuf ProtoContractAttribute                 null                throw new ArgumentException  Type has no ProtoContract     source               if Object ReferenceEquals source  null                 return default T              IFormatter formatter   ProtoBuf Serializer CreateFormatter lt T gt         using  Stream stream   new MemoryStream                  formatter Serialize stream  source           stream Seek 0  SeekOrigin Begin           return  T formatter Deserialize stream             This checks for the presence of a  ProtoContract  attribute and uses protobufs own formatter to serialize the object

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As nearly all of the answers to this question have been unsatisfactory or plainly don t work in my situation  I have authored AnyClone which is entirely implemented with reflection and solved all of the needs here  I was unable to get serialization to work in a complicated scenario with complex structure  and IClonable is less than ideal - in fact it shouldn t even be necessary   Standard ignore attributes are supported using  IgnoreDataMember    NonSerialized   Supports complex collections  properties without setters  readonly fields etc   I hope it helps someone else out there who ran into the same problems I did

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Simple extension method to copy all the public properties  Works for any objects and does not require class to be  Serializable   Can be extended for other access level   public static void CopyTo  this object S  object T         foreach  var pS in S GetType   GetProperties                   foreach  var pT in T GetType   GetProperties                           if  pT Name    pS Name   continue                pT GetSetMethod     Invoke  T  new object                  pS GetGetMethod   Invoke  S  null

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As I couldn t find a cloner that meets all my requirements in different projects  I created a deep cloner that can be configured and adapted to different code structures instead of adapting my code to meet the cloners requirements  Its achieved by adding annotations to the code that shall be cloned or you just leave the code as it is to have the default behaviour  It uses reflection  type caches and is based on fasterflect  The cloning process is very fast for a huge amount of data and a high object hierarchy  compared to other reflection serialization based algorithms     https   github com kalisohn CloneBehave  Also available as a nuget package  https   www nuget org packages Clone Behave 1 0 0  For example  The following code will deepClone Address  but only perform a shallow copy of the  currentJob field    public class Person       DeepClone DeepCloneBehavior Shallow     private Job  currentJob           public string Name   get  set       public Job CurrentJob           get  return  currentJob        set   currentJob   value           public Person Manager   get  set       public class Address            public Person PersonLivingHere   get  set       Address adr   new Address    adr PersonLivingHere   new Person  John    adr PersonLivingHere BestFriend   new Person  James    adr PersonLivingHere CurrentJob   new Job  Programmer     Address adrClone   adr Clone       RESULT adr PersonLivingHere    adrClone PersonLivingHere   false adr PersonLivingHere Manager    adrClone PersonLivingHere Manager   false adr PersonLivingHere CurrentJob    adrClone PersonLivingHere CurrentJob   true adr PersonLivingHere CurrentJob AnyProperty    adrClone PersonLivingHere CurrentJob AnyProperty   true

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Basically you need to implement ICloneable interface and then realize object structure copying   If it s deep copy of all members  you need to insure  not relating on solution you choose  that all children are clonable as well   Sometimes you need to be aware of some restriction during this process  for example if you copying the ORM objects most of frameworks allow only one object attached to the session and you MUST NOT make clones of this object  or if it s possible you need to care about session attaching of these objects    Cheers

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This method solved the problem for me   private static MyObj DeepCopy MyObj source                         var DeserializeSettings   new JsonSerializerSettings   ObjectCreationHandling   ObjectCreationHandling Replace                 return JsonConvert DeserializeObject lt MyObj  gt  JsonConvert SerializeObject source   DeserializeSettings                Use it like this  MyObj a   DeepCopy b

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Whereas one approach is to implement the ICloneable interface  described here  so I won t regurgitate   here s a nice deep clone object copier I found on The Code Project a while ago and incorporated it into our code  As mentioned elsewhere  it requires your objects to be serializable  using System  using System IO  using System Runtime Serialization  using System Runtime Serialization Formatters Binary        lt summary gt      Reference Article http   www codeproject com KB tips SerializedObjectCloner aspx     Provides a method for performing a deep copy of an object      Binary Serialization is used to perform the copy       lt  summary gt  public static class ObjectCopier            lt summary gt          Perform a deep copy of the object via serialization           lt  summary gt           lt typeparam name  quot T quot  gt The type of object being copied  lt  typeparam gt           lt param name  quot source quot  gt The object instance to copy  lt  param gt           lt returns gt A deep copy of the object  lt  returns gt      public static T Clone lt T gt  T source                if   typeof T  IsSerializable                        throw new ArgumentException  quot The type must be serializable  quot   nameof source                          Don t serialize a null object  simply return the default for that object         if  ReferenceEquals self  null   return default           using var Stream stream   new MemoryStream            IFormatter formatter   new BinaryFormatter            formatter Serialize stream  source           stream Seek 0  SeekOrigin Begin           return  T formatter Deserialize stream            The idea is that it serializes your object and then deserializes it into a fresh object  The benefit is that you don t have to concern yourself about cloning everything when an object gets too complex  In case of you prefer to use the new extension methods of C  3 0  change the method to have the following signature  public static T Clone lt T gt  this T source                 Now the method call simply becomes objectBeingCloned Clone     EDIT  January 10 2015  Thought I d revisit this  to mention I recently started using  Newtonsoft  Json to do this  it should be lighter  and avoids the overhead of  Serializable  tags   NB  atconway has pointed out in the comments that private members are not cloned using the JSON method       lt summary gt      Perform a deep Copy of the object  using Json as a serialization method  NOTE  Private members are not cloned using this method       lt  summary gt       lt typeparam name  quot T quot  gt The type of object being copied  lt  typeparam gt       lt param name  quot source quot  gt The object instance to copy  lt  param gt       lt returns gt The copied object  lt  returns gt  public static T CloneJson lt T gt  this T source                       Don t serialize a null object  simply return the default for that object     if  ReferenceEquals self  null   return default          initialize inner objects individually        for example in default constructor some list property initialized with some values         but in  source  these items are cleaned -        without ObjectCreationHandling Replace default constructor values will be added to result     var deserializeSettings   new JsonSerializerSettings  ObjectCreationHandling   ObjectCreationHandling Replace        return JsonConvert DeserializeObject lt T gt  JsonConvert SerializeObject source   deserializeSettings

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In general  you implement the ICloneable interface and implement Clone yourself  C  objects have a built-in MemberwiseClone method that performs a shallow copy that can help you out for all the primitives   For a deep copy  there is no way it can know how to automatically do it

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I came up with this to overcome a  NET shortcoming having to manually deep copy List lt T    I use this   static public IEnumerable lt SpotPlacement gt  CloneList List lt SpotPlacement gt  spotPlacements        foreach  SpotPlacement sp in spotPlacements                yield return  SpotPlacement sp Clone              And at another place   public object Clone         OrderItem newOrderItem   new OrderItem                newOrderItem  exactPlacements AddRange SpotPlacement CloneList  exactPlacements                return newOrderItem      I tried to come up with oneliner that does this  but it s not possible  due to yield not working inside anonymous method blocks   Better still  use generic List lt T  cloner   class Utility lt T gt  where T   ICloneable       static public IEnumerable lt T gt  CloneList List lt T gt  tl                foreach  T t in tl                        yield return  T t Clone

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Q  Why would I choose this answer   Choose this answer if you want the fastest speed  NET is capable of  Ignore this answer if you want a really  really easy method of cloning   In other words  go with another answer unless you have a performance bottleneck that needs fixing  and you can prove it with a profiler  10x faster than other methods The following method of performing a deep clone is   10x faster than anything that involves serialization deserialization  Pretty darn close to the theoretical maximum speed  NET is capable of   And the method     For ultimate speed  you can use Nested MemberwiseClone to do a deep copy  Its almost the same speed as copying a value struct  and is much faster than  a  reflection or  b  serialization  as described in other answers on this page   Note that if you use Nested MemberwiseClone for a deep copy  you have to manually implement a ShallowCopy for each nested level in the class  and a DeepCopy which calls all said ShallowCopy methods to create a complete clone  This is simple  only a few lines in total  see the demo code below  Here is the output of the code showing the relative performance difference for 100 000 clones   1 08 seconds for Nested MemberwiseClone on nested structs 4 77 seconds for Nested MemberwiseClone on nested classes 39 93 seconds for Serialization Deserialization  Using Nested MemberwiseClone on a class almost as fast as copying a struct  and copying a struct is pretty darn close to the theoretical maximum speed  NET is capable of  Demo 1 of shallow and deep copy  using classes and MemberwiseClone    Create Bob     Bob Age 30  Bob Purchase Description Lamborghini   Clone Bob  gt  gt  BobsSon   Adjust BobsSon details     BobsSon Age 2  BobsSon Purchase Description Toy car   Proof of deep copy  If BobsSon is a true clone  then adjusting BobsSon details will not affect Bob      Bob Age 30  Bob Purchase Description Lamborghini   Elapsed time  00 00 04 7795670 30000000  Demo 2 of shallow and deep copy  using structs and value copying    Create Bob     Bob Age 30  Bob Purchase Description Lamborghini   Clone Bob  gt  gt  BobsSon   Adjust BobsSon details      BobsSon Age 2  BobsSon Purchase Description Toy car   Proof of deep copy  If BobsSon is a true clone  then adjusting BobsSon details will not affect Bob      Bob Age 30  Bob Purchase Description Lamborghini   Elapsed time  00 00 01 0875454 30000000  Demo 3 of deep copy  using class and serialize deserialize    Elapsed time  00 00 39 9339425 30000000  To understand how to do a deep copy using MemberwiseCopy  here is the demo project that was used to generate the times above     Nested MemberwiseClone example      Added to demo how to deep copy a reference class   Serializable     Not required if using MemberwiseClone  only used for speed comparison using serialization  public class Person       public Person int age  string description                this Age   age          this Purchase Description   description             Serializable     Not required if using MemberwiseClone     public class PurchaseType               public string Description          public PurchaseType ShallowCopy                         return  PurchaseType this MemberwiseClone                        public PurchaseType Purchase   new PurchaseType        public int Age         Add this if using nested MemberwiseClone         This is a class  which is a reference type  so cloning is more difficult      public Person ShallowCopy                 return  Person this MemberwiseClone                 Add this if using nested MemberwiseClone         This is a class  which is a reference type  so cloning is more difficult      public Person DeepCopy                        Clone the root             Person other    Person  this MemberwiseClone                       then clone the nested class          other Purchase   this Purchase ShallowCopy            return other             Added to demo how to copy a value struct  this is easy - a deep copy happens by default  public struct PersonStruct       public PersonStruct int age  string description                this Age   age          this Purchase Description   description            public struct PurchaseType               public string Description            public PurchaseType Purchase      public int Age         This is a struct  which is a value type  so everything is a clone by default      public PersonStruct ShallowCopy                 return  PersonStruct this               This is a struct  which is a value type  so everything is a clone by default      public PersonStruct DeepCopy                 return  PersonStruct this             Added only for a speed comparison  public class MyDeepCopy       public static T DeepCopy lt T gt  T obj                object result   null          using  var ms   new MemoryStream                          var formatter   new BinaryFormatter                formatter Serialize ms  obj               ms Position   0              result    T formatter Deserialize ms               ms Close                      return  T result           Then  call the demo from main  void MyMain string   args                  Console Write  quot Demo 1 of shallow and deep copy  using classes and MemberwiseCopy  n quot            var Bob   new Person 30   quot Lamborghini quot            Console Write  quot   Create Bob n quot            Console Write  quot     Bob Age  0   Bob Purchase Description  1  n quot   Bob Age  Bob Purchase Description           Console Write  quot   Clone Bob  gt  gt  BobsSon n quot            var BobsSon   Bob DeepCopy            Console Write  quot   Adjust BobsSon details n quot            BobsSon Age   2          BobsSon Purchase Description    quot Toy car quot           Console Write  quot     BobsSon Age  0   BobsSon Purchase Description  1  n quot   BobsSon Age  BobsSon Purchase Description           Console Write  quot   Proof of deep copy  If BobsSon is a true clone  then adjusting BobsSon details will not affect Bob  n quot            Console Write  quot     Bob Age  0   Bob Purchase Description  1  n quot   Bob Age  Bob Purchase Description           Debug Assert Bob Age    30           Debug Assert Bob Purchase Description     quot Lamborghini quot            var sw   new Stopwatch            sw Start            int total   0          for  int i   0  i  lt  100000  i                          var n   Bob DeepCopy                total    n Age                    Console Write  quot   Elapsed time   0   1  n n quot   sw Elapsed  total                                      Console Write  quot Demo 2 of shallow and deep copy  using structs  n quot            var Bob   new PersonStruct 30   quot Lamborghini quot            Console Write  quot   Create Bob n quot            Console Write  quot     Bob Age  0   Bob Purchase Description  1  n quot   Bob Age  Bob Purchase Description           Console Write  quot   Clone Bob  gt  gt  BobsSon n quot            var BobsSon   Bob DeepCopy            Console Write  quot   Adjust BobsSon details  n quot            BobsSon Age   2          BobsSon Purchase Description    quot Toy car quot           Console Write  quot     BobsSon Age  0   BobsSon Purchase Description  1  n quot   BobsSon Age  BobsSon Purchase Description           Console Write  quot   Proof of deep copy  If BobsSon is a true clone  then adjusting BobsSon details will not affect Bob  n quot            Console Write  quot     Bob Age  0   Bob Purchase Description  1  n quot   Bob Age  Bob Purchase Description                           Debug Assert Bob Age    30           Debug Assert Bob Purchase Description     quot Lamborghini quot            var sw   new Stopwatch            sw Start            int total   0          for  int i   0  i  lt  100000  i                          var n   Bob DeepCopy                total    n Age                    Console Write  quot   Elapsed time   0   1  n n quot   sw Elapsed  total                       Console Write  quot Demo 3 of deep copy  using class and serialize deserialize  n quot            int total   0          var sw   new Stopwatch            sw Start            var Bob   new Person 30   quot Lamborghini quot            for  int i   0  i  lt  100000  i                          var BobsSon   MyDeepCopy DeepCopy lt Person gt  Bob               total    BobsSon Age                    Console Write  quot   Elapsed time   0   1  n quot   sw Elapsed  total             Console ReadKey       Again  note that if you use Nested MemberwiseClone for a deep copy  you have to manually implement a ShallowCopy for each nested level in the class  and a DeepCopy which calls all said ShallowCopy methods to create a complete clone  This is simple  only a few lines in total  see the demo code above  Value types vs  References Types Note that when it comes to cloning an object  there is is a big difference between a  quot struct quot  and a  quot class quot    If you have a  quot struct quot   it s a value type so you can just copy it  and the contents will be cloned  but it will only make a shallow clone unless you use the techniques in this post   If you have a  quot class quot   it s a reference type  so if you copy it  all you are doing is copying the pointer to it  To create a true clone  you have to be more creative  and use differences between value types and references types which creates another copy of the original object in memory   See differences between value types and references types  Checksums to aid in debugging  Cloning objects incorrectly can lead to very difficult-to-pin-down bugs  In production code  I tend to implement a checksum to double check that the object has been cloned properly  and hasn t been corrupted by another reference to it  This checksum can be switched off in Release mode  I find this method quite useful  often  you only want to clone parts of the object  not the entire thing   Really useful for decoupling many threads from many other threads One excellent use case for this code is feeding clones of a nested class or struct into a queue  to implement the producer   consumer pattern   We can have one   or more  threads modifying a class that they own  then pushing a complete copy of this class into a ConcurrentQueue  We then have one  or more  threads pulling copies of these classes out and dealing with them   This works extremely well in practice  and allows us to decouple many threads  the producers  from one or more threads  the consumers   And this method is blindingly fast too  if we use nested structs  it s 35x faster than serializing deserializing nested classes  and allows us to take advantage of all of the threads available on the machine  Update Apparently  ExpressMapper is as fast  if not faster  than hand coding such as above  I might have to see how they compare with a profiler

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Shortest way but need dependency   using Newtonsoft Json      public static T Clone lt T gt  T source    gt          JsonConvert DeserializeObject lt T gt  JsonConvert SerializeObject source

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The reason not to use ICloneable is not because it doesn t have a generic interface   The reason not to use it is because it s vague   It doesn t make clear whether you re getting a shallow or a deep copy  that s up to the implementer   Yes  MemberwiseClone makes a shallow copy  but the opposite of MemberwiseClone isn t Clone  it would be  perhaps  DeepClone  which doesn t exist   When you use an object through its ICloneable interface  you can t know which kind of cloning the underlying object performs    And XML comments won t make it clear  because you ll get the interface comments rather than the ones on the object s Clone method    What I usually do is simply make a Copy method that does exactly what I want

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C  Extension that ll support for  not ISerializable  types too    public static class AppExtensions                                                                                 public static T DeepClone lt T gt  this T a                      using  var stream   new MemoryStream                                var serializer   new System Xml Serialization XmlSerializer typeof T                    serializer Serialize stream  a                  stream Position   0                 return  T serializer Deserialize stream                                                                                                  Usage         var obj2   obj1 DeepClone

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Simple extension method to copy all the public properties  Works for any objects and does not require class to be  Serializable   Can be extended for other access level   public static void CopyTo  this object S  object T         foreach  var pS in S GetType   GetProperties                   foreach  var pT in T GetType   GetProperties                           if  pT Name    pS Name   continue                pT GetSetMethod     Invoke  T  new object                  pS GetGetMethod   Invoke  S  null

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Ok  there are some obvious example with reflection in this post  BUT reflection is usually slow  until you start to cache it properly   if you ll cache it properly  than it ll deep clone 1000000 object by 4 6s  measured by Watcher    static readonly Dictionary lt Type  PropertyInfo   gt  ProperyList   new Dictionary lt Type  PropertyInfo   gt       than you take cached properties or add new to dictionary and use them simply  foreach  var prop in propList            var value   prop GetValue source  null              prop SetValue copyInstance  value  null       full code check in my post in another answer  https   stackoverflow com a 34365709 4711853

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Ok  there are some obvious example with reflection in this post  BUT reflection is usually slow  until you start to cache it properly   if you ll cache it properly  than it ll deep clone 1000000 object by 4 6s  measured by Watcher    static readonly Dictionary lt Type  PropertyInfo   gt  ProperyList   new Dictionary lt Type  PropertyInfo   gt       than you take cached properties or add new to dictionary and use them simply  foreach  var prop in propList            var value   prop GetValue source  null              prop SetValue copyInstance  value  null       full code check in my post in another answer  https   stackoverflow com a 34365709 4711853

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Q  Why would I choose this answer   Choose this answer if you want the fastest speed  NET is capable of  Ignore this answer if you want a really  really easy method of cloning   In other words  go with another answer unless you have a performance bottleneck that needs fixing  and you can prove it with a profiler  10x faster than other methods The following method of performing a deep clone is   10x faster than anything that involves serialization deserialization  Pretty darn close to the theoretical maximum speed  NET is capable of   And the method     For ultimate speed  you can use Nested MemberwiseClone to do a deep copy  Its almost the same speed as copying a value struct  and is much faster than  a  reflection or  b  serialization  as described in other answers on this page   Note that if you use Nested MemberwiseClone for a deep copy  you have to manually implement a ShallowCopy for each nested level in the class  and a DeepCopy which calls all said ShallowCopy methods to create a complete clone  This is simple  only a few lines in total  see the demo code below  Here is the output of the code showing the relative performance difference for 100 000 clones   1 08 seconds for Nested MemberwiseClone on nested structs 4 77 seconds for Nested MemberwiseClone on nested classes 39 93 seconds for Serialization Deserialization  Using Nested MemberwiseClone on a class almost as fast as copying a struct  and copying a struct is pretty darn close to the theoretical maximum speed  NET is capable of  Demo 1 of shallow and deep copy  using classes and MemberwiseClone    Create Bob     Bob Age 30  Bob Purchase Description Lamborghini   Clone Bob  gt  gt  BobsSon   Adjust BobsSon details     BobsSon Age 2  BobsSon Purchase Description Toy car   Proof of deep copy  If BobsSon is a true clone  then adjusting BobsSon details will not affect Bob      Bob Age 30  Bob Purchase Description Lamborghini   Elapsed time  00 00 04 7795670 30000000  Demo 2 of shallow and deep copy  using structs and value copying    Create Bob     Bob Age 30  Bob Purchase Description Lamborghini   Clone Bob  gt  gt  BobsSon   Adjust BobsSon details      BobsSon Age 2  BobsSon Purchase Description Toy car   Proof of deep copy  If BobsSon is a true clone  then adjusting BobsSon details will not affect Bob      Bob Age 30  Bob Purchase Description Lamborghini   Elapsed time  00 00 01 0875454 30000000  Demo 3 of deep copy  using class and serialize deserialize    Elapsed time  00 00 39 9339425 30000000  To understand how to do a deep copy using MemberwiseCopy  here is the demo project that was used to generate the times above     Nested MemberwiseClone example      Added to demo how to deep copy a reference class   Serializable     Not required if using MemberwiseClone  only used for speed comparison using serialization  public class Person       public Person int age  string description                this Age   age          this Purchase Description   description             Serializable     Not required if using MemberwiseClone     public class PurchaseType               public string Description          public PurchaseType ShallowCopy                         return  PurchaseType this MemberwiseClone                        public PurchaseType Purchase   new PurchaseType        public int Age         Add this if using nested MemberwiseClone         This is a class  which is a reference type  so cloning is more difficult      public Person ShallowCopy                 return  Person this MemberwiseClone                 Add this if using nested MemberwiseClone         This is a class  which is a reference type  so cloning is more difficult      public Person DeepCopy                        Clone the root             Person other    Person  this MemberwiseClone                       then clone the nested class          other Purchase   this Purchase ShallowCopy            return other             Added to demo how to copy a value struct  this is easy - a deep copy happens by default  public struct PersonStruct       public PersonStruct int age  string description                this Age   age          this Purchase Description   description            public struct PurchaseType               public string Description            public PurchaseType Purchase      public int Age         This is a struct  which is a value type  so everything is a clone by default      public PersonStruct ShallowCopy                 return  PersonStruct this               This is a struct  which is a value type  so everything is a clone by default      public PersonStruct DeepCopy                 return  PersonStruct this             Added only for a speed comparison  public class MyDeepCopy       public static T DeepCopy lt T gt  T obj                object result   null          using  var ms   new MemoryStream                          var formatter   new BinaryFormatter                formatter Serialize ms  obj               ms Position   0              result    T formatter Deserialize ms               ms Close                      return  T result           Then  call the demo from main  void MyMain string   args                  Console Write  quot Demo 1 of shallow and deep copy  using classes and MemberwiseCopy  n quot            var Bob   new Person 30   quot Lamborghini quot            Console Write  quot   Create Bob n quot            Console Write  quot     Bob Age  0   Bob Purchase Description  1  n quot   Bob Age  Bob Purchase Description           Console Write  quot   Clone Bob  gt  gt  BobsSon n quot            var BobsSon   Bob DeepCopy            Console Write  quot   Adjust BobsSon details n quot            BobsSon Age   2          BobsSon Purchase Description    quot Toy car quot           Console Write  quot     BobsSon Age  0   BobsSon Purchase Description  1  n quot   BobsSon Age  BobsSon Purchase Description           Console Write  quot   Proof of deep copy  If BobsSon is a true clone  then adjusting BobsSon details will not affect Bob  n quot            Console Write  quot     Bob Age  0   Bob Purchase Description  1  n quot   Bob Age  Bob Purchase Description           Debug Assert Bob Age    30           Debug Assert Bob Purchase Description     quot Lamborghini quot            var sw   new Stopwatch            sw Start            int total   0          for  int i   0  i  lt  100000  i                          var n   Bob DeepCopy                total    n Age                    Console Write  quot   Elapsed time   0   1  n n quot   sw Elapsed  total                                      Console Write  quot Demo 2 of shallow and deep copy  using structs  n quot            var Bob   new PersonStruct 30   quot Lamborghini quot            Console Write  quot   Create Bob n quot            Console Write  quot     Bob Age  0   Bob Purchase Description  1  n quot   Bob Age  Bob Purchase Description           Console Write  quot   Clone Bob  gt  gt  BobsSon n quot            var BobsSon   Bob DeepCopy            Console Write  quot   Adjust BobsSon details  n quot            BobsSon Age   2          BobsSon Purchase Description    quot Toy car quot           Console Write  quot     BobsSon Age  0   BobsSon Purchase Description  1  n quot   BobsSon Age  BobsSon Purchase Description           Console Write  quot   Proof of deep copy  If BobsSon is a true clone  then adjusting BobsSon details will not affect Bob  n quot            Console Write  quot     Bob Age  0   Bob Purchase Description  1  n quot   Bob Age  Bob Purchase Description                           Debug Assert Bob Age    30           Debug Assert Bob Purchase Description     quot Lamborghini quot            var sw   new Stopwatch            sw Start            int total   0          for  int i   0  i  lt  100000  i                          var n   Bob DeepCopy                total    n Age                    Console Write  quot   Elapsed time   0   1  n n quot   sw Elapsed  total                       Console Write  quot Demo 3 of deep copy  using class and serialize deserialize  n quot            int total   0          var sw   new Stopwatch            sw Start            var Bob   new Person 30   quot Lamborghini quot            for  int i   0  i  lt  100000  i                          var BobsSon   MyDeepCopy DeepCopy lt Person gt  Bob               total    BobsSon Age                    Console Write  quot   Elapsed time   0   1  n quot   sw Elapsed  total             Console ReadKey       Again  note that if you use Nested MemberwiseClone for a deep copy  you have to manually implement a ShallowCopy for each nested level in the class  and a DeepCopy which calls all said ShallowCopy methods to create a complete clone  This is simple  only a few lines in total  see the demo code above  Value types vs  References Types Note that when it comes to cloning an object  there is is a big difference between a  quot struct quot  and a  quot class quot    If you have a  quot struct quot   it s a value type so you can just copy it  and the contents will be cloned  but it will only make a shallow clone unless you use the techniques in this post   If you have a  quot class quot   it s a reference type  so if you copy it  all you are doing is copying the pointer to it  To create a true clone  you have to be more creative  and use differences between value types and references types which creates another copy of the original object in memory   See differences between value types and references types  Checksums to aid in debugging  Cloning objects incorrectly can lead to very difficult-to-pin-down bugs  In production code  I tend to implement a checksum to double check that the object has been cloned properly  and hasn t been corrupted by another reference to it  This checksum can be switched off in Release mode  I find this method quite useful  often  you only want to clone parts of the object  not the entire thing   Really useful for decoupling many threads from many other threads One excellent use case for this code is feeding clones of a nested class or struct into a queue  to implement the producer   consumer pattern   We can have one   or more  threads modifying a class that they own  then pushing a complete copy of this class into a ConcurrentQueue  We then have one  or more  threads pulling copies of these classes out and dealing with them   This works extremely well in practice  and allows us to decouple many threads  the producers  from one or more threads  the consumers   And this method is blindingly fast too  if we use nested structs  it s 35x faster than serializing deserializing nested classes  and allows us to take advantage of all of the threads available on the machine  Update Apparently  ExpressMapper is as fast  if not faster  than hand coding such as above  I might have to see how they compare with a profiler

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Disclaimer  I m the author of the mentioned package   I was surprised how the top answers to this question in 2019 still use serialization or reflection    Serialization is limiting  requires attributes  specific constructors  etc   and is very slow  BinaryFormatter requires the Serializable attribute  JsonConverter requires a parameterless constructor or attributes  neither handle read only fields or interfaces very well and both are 10-30x slower than necessary   Expression Trees  You can instead use Expression Trees or Reflection Emit to generate cloning code only once  then use that compiled code instead of slow reflection or serialization   Having come across the problem myself and seeing no satisfactory solution  I decided to create a package that does just that and works with every type and is a almost as fast as custom written code   You can find the project on GitHub  https   github com marcelltoth ObjectCloner  Usage  You can install it from NuGet  Either get the ObjectCloner package and use it as   var clone   ObjectCloner DeepClone original     or if you don t mind polluting your object type with extensions get ObjectCloner Extensions as well and write   var clone   original DeepClone      Performance  A simple benchmark of cloning a class hierarchy showed performance  3x faster than using Reflection   12x faster than Newtonsoft Json serialization and  36x faster than the highly suggested BinaryFormatter

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Disclaimer  I m the author of the mentioned package   I was surprised how the top answers to this question in 2019 still use serialization or reflection    Serialization is limiting  requires attributes  specific constructors  etc   and is very slow  BinaryFormatter requires the Serializable attribute  JsonConverter requires a parameterless constructor or attributes  neither handle read only fields or interfaces very well and both are 10-30x slower than necessary   Expression Trees  You can instead use Expression Trees or Reflection Emit to generate cloning code only once  then use that compiled code instead of slow reflection or serialization   Having come across the problem myself and seeing no satisfactory solution  I decided to create a package that does just that and works with every type and is a almost as fast as custom written code   You can find the project on GitHub  https   github com marcelltoth ObjectCloner  Usage  You can install it from NuGet  Either get the ObjectCloner package and use it as   var clone   ObjectCloner DeepClone original     or if you don t mind polluting your object type with extensions get ObjectCloner Extensions as well and write   var clone   original DeepClone      Performance  A simple benchmark of cloning a class hierarchy showed performance  3x faster than using Reflection   12x faster than Newtonsoft Json serialization and  36x faster than the highly suggested BinaryFormatter

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Keep things simple and use AutoMapper as others mentioned  it s a simple little library to map one object to another    To copy an object to another with the same type  all you need is three lines of code   MyType source   new MyType    Mapper CreateMap lt MyType  MyType gt     MyType target   Mapper Map lt MyType  MyType gt  source     The target object is now a copy of the source object  Not simple enough  Create an extension method to use everywhere in your solution   public static T Copy lt T gt  this T source        T copy   default T       Mapper CreateMap lt T  T gt         copy   Mapper Map lt T  T gt  source       return copy      The extension method can be used as follow   MyType copy   source Copy

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As nearly all of the answers to this question have been unsatisfactory or plainly don t work in my situation  I have authored AnyClone which is entirely implemented with reflection and solved all of the needs here  I was unable to get serialization to work in a complicated scenario with complex structure  and IClonable is less than ideal - in fact it shouldn t even be necessary   Standard ignore attributes are supported using  IgnoreDataMember    NonSerialized   Supports complex collections  properties without setters  readonly fields etc   I hope it helps someone else out there who ran into the same problems I did

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Using System Text Json   https   devblogs microsoft com dotnet try-the-new-system-text-json-apis   public static T DeepCopy lt T gt  this T source        return source    null   default   JsonSerializer Parse lt T gt  JsonSerializer ToString source        The new API is using Span lt T gt   This should be fast  would be nice to do some benchmarks   Note  there s no need for ObjectCreationHandling Replace like in Json NET as it will replace collection values by default  You should forget about Json NET now as everything is going to be replaced with the new official API   I m not sure this will work with private fields

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Well I was having problems using ICloneable in Silverlight  but I liked the idea of seralization  I can seralize XML  so I did this   static public class SerializeHelper         Michael White  Holly Springs Consulting  2009       michael hollyspringsconsulting com     public static T DeserializeXML lt T gt  string xmlData  where T new                 if  string IsNullOrEmpty xmlData               return default T            TextReader tr   new StringReader xmlData           T DocItms   new T            XmlSerializer xms   new XmlSerializer DocItms GetType             DocItms    T xms Deserialize tr            return DocItms    null   default T    DocItms             public static string SeralizeObjectToXML lt T gt  T xmlObject                StringBuilder sbTR   new StringBuilder            XmlSerializer xmsTR   new XmlSerializer xmlObject GetType             XmlWriterSettings xwsTR   new XmlWriterSettings             XmlWriter xmwTR   XmlWriter Create sbTR  xwsTR           xmsTR Serialize xmwTR xmlObject            return sbTR ToString               public static T CloneObject lt T gt  T objClone  where T new                 string GetString   SerializeHelper SeralizeObjectToXML lt T gt  objClone           return SerializeHelper DeserializeXML lt T gt  GetString

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I like Copyconstructors like that       public AnyObject AnyObject anyObject                foreach  var property in typeof AnyObject  GetProperties                          property SetValue this  property GetValue anyObject                      foreach  var field in typeof AnyObject  GetFields                          field SetValue this  field GetValue anyObject                      If you have more things to copy add them

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Here is a deep copy implementation   public static object CloneObject object opSource          grab the type and create a new instance of that type     Type opSourceType   opSource GetType        object opTarget   CreateInstanceOfType opSourceType          grab the properties     PropertyInfo   opPropertyInfo   opSourceType GetProperties BindingFlags Public   BindingFlags NonPublic   BindingFlags Instance          iterate over the properties and if it has a  set  method assign it from the source TO the target     foreach  PropertyInfo item in opPropertyInfo                if  item CanWrite                          value types can simply be  set              if  item PropertyType IsValueType    item PropertyType IsEnum    item PropertyType Equals typeof System String                                  item SetValue opTarget  item GetValue opSource  null   null                               object complex types need to recursively call this method until the end of the tree is reached             else                               object opPropertyValue   item GetValue opSource  null                   if  opPropertyValue    null                                        item SetValue opTarget  null  null                                     else                                       item SetValue opTarget  CloneObject opPropertyValue   null                                                         return the new item     return opTarget

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how about just recasting inside a method  that should invoke basically a automatic copy constructor  T t   new T    T t2    T t     eh something like that          List lt myclass gt  cloneum          public void SomeFuncB ref List lt myclass gt   mylist                        cloneum   new List lt myclass gt                 cloneum    List  lt  myclass  gt    mylist              cloneum Add new myclass 3                 mylist   new List lt myclass gt                 seems to work to me

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C  Extension that ll support for  not ISerializable  types too    public static class AppExtensions                                                                                 public static T DeepClone lt T gt  this T a                      using  var stream   new MemoryStream                                var serializer   new System Xml Serialization XmlSerializer typeof T                    serializer Serialize stream  a                  stream Position   0                 return  T serializer Deserialize stream                                                                                                  Usage         var obj2   obj1 DeepClone

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Whereas one approach is to implement the ICloneable interface  described here  so I won t regurgitate   here s a nice deep clone object copier I found on The Code Project a while ago and incorporated it into our code  As mentioned elsewhere  it requires your objects to be serializable  using System  using System IO  using System Runtime Serialization  using System Runtime Serialization Formatters Binary        lt summary gt      Reference Article http   www codeproject com KB tips SerializedObjectCloner aspx     Provides a method for performing a deep copy of an object      Binary Serialization is used to perform the copy       lt  summary gt  public static class ObjectCopier            lt summary gt          Perform a deep copy of the object via serialization           lt  summary gt           lt typeparam name  quot T quot  gt The type of object being copied  lt  typeparam gt           lt param name  quot source quot  gt The object instance to copy  lt  param gt           lt returns gt A deep copy of the object  lt  returns gt      public static T Clone lt T gt  T source                if   typeof T  IsSerializable                        throw new ArgumentException  quot The type must be serializable  quot   nameof source                          Don t serialize a null object  simply return the default for that object         if  ReferenceEquals self  null   return default           using var Stream stream   new MemoryStream            IFormatter formatter   new BinaryFormatter            formatter Serialize stream  source           stream Seek 0  SeekOrigin Begin           return  T formatter Deserialize stream            The idea is that it serializes your object and then deserializes it into a fresh object  The benefit is that you don t have to concern yourself about cloning everything when an object gets too complex  In case of you prefer to use the new extension methods of C  3 0  change the method to have the following signature  public static T Clone lt T gt  this T source                 Now the method call simply becomes objectBeingCloned Clone     EDIT  January 10 2015  Thought I d revisit this  to mention I recently started using  Newtonsoft  Json to do this  it should be lighter  and avoids the overhead of  Serializable  tags   NB  atconway has pointed out in the comments that private members are not cloned using the JSON method       lt summary gt      Perform a deep Copy of the object  using Json as a serialization method  NOTE  Private members are not cloned using this method       lt  summary gt       lt typeparam name  quot T quot  gt The type of object being copied  lt  typeparam gt       lt param name  quot source quot  gt The object instance to copy  lt  param gt       lt returns gt The copied object  lt  returns gt  public static T CloneJson lt T gt  this T source                       Don t serialize a null object  simply return the default for that object     if  ReferenceEquals self  null   return default          initialize inner objects individually        for example in default constructor some list property initialized with some values         but in  source  these items are cleaned -        without ObjectCreationHandling Replace default constructor values will be added to result     var deserializeSettings   new JsonSerializerSettings  ObjectCreationHandling   ObjectCreationHandling Replace        return JsonConvert DeserializeObject lt T gt  JsonConvert SerializeObject source   deserializeSettings

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Here is a deep copy implementation   public static object CloneObject object opSource          grab the type and create a new instance of that type     Type opSourceType   opSource GetType        object opTarget   CreateInstanceOfType opSourceType          grab the properties     PropertyInfo   opPropertyInfo   opSourceType GetProperties BindingFlags Public   BindingFlags NonPublic   BindingFlags Instance          iterate over the properties and if it has a  set  method assign it from the source TO the target     foreach  PropertyInfo item in opPropertyInfo                if  item CanWrite                          value types can simply be  set              if  item PropertyType IsValueType    item PropertyType IsEnum    item PropertyType Equals typeof System String                                  item SetValue opTarget  item GetValue opSource  null   null                               object complex types need to recursively call this method until the end of the tree is reached             else                               object opPropertyValue   item GetValue opSource  null                   if  opPropertyValue    null                                        item SetValue opTarget  null  null                                     else                                       item SetValue opTarget  CloneObject opPropertyValue   null                                                         return the new item     return opTarget

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Deep cloning is about copying state  For  net state means fields   Let s say one have an hierarchy   static class RandomHelper       private static readonly Random random   new Random         public static int Next int maxValue    gt  random Next maxValue      class A       private readonly int random   RandomHelper Next 100        public override string ToString     gt     typeof A  Name   nameof random      random       class B   A       private readonly int random   RandomHelper Next 100        public override string ToString     gt     typeof B  Name   nameof random      random   base ToString         class C   B       private readonly int random   RandomHelper Next 100        public override string ToString     gt     typeof C  Name   nameof random      random   base ToString          Cloning can be done   static class DeepCloneExtension          consider instance fields  both public and non-public     private static readonly BindingFlags bindingFlags           BindingFlags Public   BindingFlags NonPublic   BindingFlags Instance       public static T DeepClone lt T gt  this T obj  where T   new                 var type   obj GetType            var result    T Activator CreateInstance type            do                copy all fields             foreach  var field in type GetFields bindingFlags                   field SetValue result  field GetValue obj               for every level of hierarchy         while   type   type BaseType     typeof object             return result            Demo1   Console WriteLine new C     Console WriteLine new C      var c   new C    Console WriteLine    Environment NewLine Image   c  Environment NewLine      Console WriteLine new C     Console WriteLine new C      Console WriteLine    Environment NewLine Clone   c DeepClone    Environment NewLine      Console WriteLine new C     Console WriteLine new C       Result   C random   92 B random   66 A random   71 C random   36 B random   64 A random   17  Image  C random   96 B random   18 A random   46  C random   60 B random   7 A random   37 C random   78 B random   11 A random   18  Clone  C random   96 B random   18 A random   46  C random   33 B random   63 A random   38 C random   4 B random   5 A random   79   Notice  all new objects have random values for random field  but clone exactly matches the image  Demo2   class D       public event EventHandler Event      public void RaiseEvent     gt  Event  Invoke this  EventArgs Empty              var image   new D    Console WriteLine   Created obj   image GetHashCode        image Event     sender  e    gt  Console WriteLine   Event from obj   sender GetHashCode       Console WriteLine   Subscribed to event of obj   image GetHashCode        image RaiseEvent    image RaiseEvent     var clone   image DeepClone    Console WriteLine   obj   image GetHashCode    cloned to obj   clone GetHashCode        clone RaiseEvent    image RaiseEvent      Result   Created obj  46104728 Subscribed to event of obj  46104728 Event from obj  46104728 Event from obj  46104728 obj  46104728 cloned to obj  12289376 Event from obj  12289376 Event from obj  46104728   Notice  event backing field is copied too and client is subscribed to clone s event too

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Whereas one approach is to implement the ICloneable interface  described here  so I won t regurgitate   here s a nice deep clone object copier I found on The Code Project a while ago and incorporated it into our code  As mentioned elsewhere  it requires your objects to be serializable  using System  using System IO  using System Runtime Serialization  using System Runtime Serialization Formatters Binary        lt summary gt      Reference Article http   www codeproject com KB tips SerializedObjectCloner aspx     Provides a method for performing a deep copy of an object      Binary Serialization is used to perform the copy       lt  summary gt  public static class ObjectCopier            lt summary gt          Perform a deep copy of the object via serialization           lt  summary gt           lt typeparam name  quot T quot  gt The type of object being copied  lt  typeparam gt           lt param name  quot source quot  gt The object instance to copy  lt  param gt           lt returns gt A deep copy of the object  lt  returns gt      public static T Clone lt T gt  T source                if   typeof T  IsSerializable                        throw new ArgumentException  quot The type must be serializable  quot   nameof source                          Don t serialize a null object  simply return the default for that object         if  ReferenceEquals self  null   return default           using var Stream stream   new MemoryStream            IFormatter formatter   new BinaryFormatter            formatter Serialize stream  source           stream Seek 0  SeekOrigin Begin           return  T formatter Deserialize stream            The idea is that it serializes your object and then deserializes it into a fresh object  The benefit is that you don t have to concern yourself about cloning everything when an object gets too complex  In case of you prefer to use the new extension methods of C  3 0  change the method to have the following signature  public static T Clone lt T gt  this T source                 Now the method call simply becomes objectBeingCloned Clone     EDIT  January 10 2015  Thought I d revisit this  to mention I recently started using  Newtonsoft  Json to do this  it should be lighter  and avoids the overhead of  Serializable  tags   NB  atconway has pointed out in the comments that private members are not cloned using the JSON method       lt summary gt      Perform a deep Copy of the object  using Json as a serialization method  NOTE  Private members are not cloned using this method       lt  summary gt       lt typeparam name  quot T quot  gt The type of object being copied  lt  typeparam gt       lt param name  quot source quot  gt The object instance to copy  lt  param gt       lt returns gt The copied object  lt  returns gt  public static T CloneJson lt T gt  this T source                       Don t serialize a null object  simply return the default for that object     if  ReferenceEquals self  null   return default          initialize inner objects individually        for example in default constructor some list property initialized with some values         but in  source  these items are cleaned -        without ObjectCreationHandling Replace default constructor values will be added to result     var deserializeSettings   new JsonSerializerSettings  ObjectCreationHandling   ObjectCreationHandling Replace        return JsonConvert DeserializeObject lt T gt  JsonConvert SerializeObject source   deserializeSettings

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Create an extension  public static T Clone lt T gt  this T theObject        string jsonData   JsonConvert SerializeObject theObject       return JsonConvert DeserializeObject lt T gt  jsonData      And call it like this  NewObject   OldObject Clone

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To clone your class object you can use the Object MemberwiseClone method   just add this function to your class    public class yourClass                              public yourClass DeepCopy                 yourClass othercopy    yourClass this MemberwiseClone            return othercopy            then to perform a deep independant copy  just call the DeepCopy method    yourClass newLine   oldLine DeepCopy      hope this helps

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I know that this question and answer sits here for a while and following is not quite answer but rather observation  to which I came across recently when I was checking whether indeed privates are not being cloned  I wouldn t be myself if I have not    when I happily copy-pasted  johnc updated answer   I simply made myself extension method  which is pretty much copy-pasted form aforementioned answer    public static class CloneThroughJsonExtension       private static readonly JsonSerializerSettings DeserializeSettings   new JsonSerializerSettings   ObjectCreationHandling   ObjectCreationHandling Replace         public static T CloneThroughJson lt T gt  this T source                return ReferenceEquals source  null    default T    JsonConvert DeserializeObject lt T gt  JsonConvert SerializeObject source   DeserializeSettings             and dropped naively class like this  in fact there was more of those but they are unrelated    public class WhatTheHeck       public string PrivateSet   get  private set       matches ctor param name      public string GetOnly   get       matches ctor param name      private readonly string  indirectField      public string Indirect   gt    Inception of    indirectField        matches ctor param name     public string RealIndirectFieldVaule   gt   indirectField       public WhatTheHeck string privateSet  string getOnly  string indirect                PrivateSet   privateSet          GetOnly   getOnly           indirectField   indirect            and code like this   var clone   new WhatTheHeck  Private-Set-Prop cloned     Get-Only-Prop cloned     Indirect-Field clonned    CloneThroughJson    Console WriteLine   1   clone PrivateSet     Console WriteLine   2   clone GetOnly     Console WriteLine   3 1   clone Indirect     Console WriteLine   3 2   clone RealIndirectFieldVaule       resulted in   1  Private-Set-Prop cloned  2  Get-Only-Prop cloned  3 1  Inception of  Inception of  Indirect-Field cloned  3 2  Inception of  Indirect-Field cloned    I was whole like  WHAT THE F    so I grabbed Newtonsoft Json Github repo and started to dig  What it comes out  is that  while deserializing a type which happens to have only one ctor and its param names match  case insensitive  public property names they will be passed to ctor as those params  Some clues can be found in the code here and here   Bottom line  I know that it is rather not common case and example code is bit abusive  but hey  It got me by surprise when I was checking whether there is any dragon waiting in the bushes to jump out and bite me in the ass

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Shortest way but need dependency   using Newtonsoft Json      public static T Clone lt T gt  T source    gt          JsonConvert DeserializeObject lt T gt  JsonConvert SerializeObject source

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I prefer a copy constructor to a clone  The intent is clearer

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The best is to implement an extension method like  public static T DeepClone lt T gt  this T originalObject       the cloning code        and then use it anywhere in the solution by  var copy   anyObject DeepClone      We can have the following three implementations    By Serialization  the shortest code  By Reflection - 5x faster By Expression Trees - 20x faster   All linked methods are well working and were deeply tested

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Basically you need to implement ICloneable interface and then realize object structure copying   If it s deep copy of all members  you need to insure  not relating on solution you choose  that all children are clonable as well   Sometimes you need to be aware of some restriction during this process  for example if you copying the ORM objects most of frameworks allow only one object attached to the session and you MUST NOT make clones of this object  or if it s possible you need to care about session attaching of these objects    Cheers

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I ve seen it implemented through reflection as well  Basically there was a method that would iterate through the members of an object and appropriately copy them to the new object  When it reached reference types or collections I think it did a recursive call on itself  Reflection is expensive  but it worked pretty well

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Yet another JSON NET answer  This version works with classes that don t implement ISerializable   public static class Cloner       public static T Clone lt T gt  T source                if  ReferenceEquals source  null               return default T            var settings   new JsonSerializerSettings   ContractResolver   new ContractResolver               return JsonConvert DeserializeObject lt T gt  JsonConvert SerializeObject source  settings   settings              class ContractResolver   DefaultContractResolver               protected override IList lt JsonProperty gt  CreateProperties Type type  MemberSerialization memberSerialization                        var props   type GetProperties BindingFlags Public   BindingFlags NonPublic   BindingFlags Instance                   Select p   gt  base CreateProperty p  memberSerialization                    Union type GetFields BindingFlags Public   BindingFlags NonPublic   BindingFlags Instance                       Select f   gt  base CreateProperty f  memberSerialization                     ToList                props ForEach p   gt    p Writable   true  p Readable   true                  return props

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Here a solution fast and easy that worked for me without relaying on Serialization Deserialization    public class MyClass       public virtual MyClass DeepClone                 var returnObj    MyClass MemberwiseClone            var type   returnObj GetType            var fieldInfoArray   type GetRuntimeFields   ToArray             foreach  var fieldInfo in fieldInfoArray                        object sourceFieldValue   fieldInfo GetValue this               if    sourceFieldValue is MyClass                                 continue                             var sourceObj    MyClass sourceFieldValue              var clonedObj   sourceObj DeepClone                fieldInfo SetValue returnObj  clonedObj                     return returnObj            EDIT  requires       using System Linq      using System Reflection    That s How I used it  public MyClass Clone MyClass theObjectIneededToClone        MyClass clonedObj   theObjectIneededToClone DeepClone

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If your Object Tree is Serializeable you could also use something like this  static public MyClass Clone MyClass myClass        MyClass clone      XmlSerializer ser   new XmlSerializer typeof MyClass    xmlAttributeOverrides       using  var ms   new MemoryStream                  ser Serialize ms  myClass           ms Position   0          clone    MyClass ser Deserialize ms             return clone      be informed that this Solution is pretty easy but it s not as performant as other solutions may be   And be sure that if the Class grows  there will still be only those fields cloned  which also get serialized

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I have created a version of the accepted answer that works with both   Serializable   and   DataContract    It has been a while since I wrote it  but if I remember correctly  DataContract  needed a different serializer   Requires System  System IO  System Runtime Serialization  System Runtime Serialization Formatters Binary  System Xml   public static class ObjectCopier             lt summary gt          Perform a deep Copy of an object that is marked with   Serializable   or   DataContract            lt  summary gt           lt typeparam name  T  gt The type of object being copied  lt  typeparam gt           lt param name  source  gt The object instance to copy  lt  param gt           lt returns gt The copied object  lt  returns gt      public static T Clone lt T gt  T source                if  typeof T  IsSerializable    true                        return CloneUsingSerializable lt T gt  source                      if  IsDataContract typeof T      true                        return CloneUsingDataContracts lt T gt  source                      throw new ArgumentException  The type must be Serializable or use DataContracts     source                     lt summary gt          Perform a deep Copy of an object that is marked with   Serializable            lt  summary gt           lt remarks gt          Found on http   stackoverflow com questions 78536 cloning-objects-in-c-sharp         Uses code found on CodeProject  which allows free use in third party apps         - http   www codeproject com KB tips SerializedObjectCloner aspx          lt  remarks gt           lt typeparam name  T  gt The type of object being copied  lt  typeparam gt           lt param name  source  gt The object instance to copy  lt  param gt           lt returns gt The copied object  lt  returns gt      public static T CloneUsingSerializable lt T gt  T source                if   typeof T  IsSerializable                        throw new ArgumentException  The type must be serializable     source                          Don t serialize a null object  simply return the default for that object         if  Object ReferenceEquals source  null                         return default T                      IFormatter formatter   new BinaryFormatter            Stream stream   new MemoryStream            using  stream                        formatter Serialize stream  source               stream Seek 0  SeekOrigin Begin               return  T formatter Deserialize stream                              lt summary gt          Perform a deep Copy of an object that is marked with   DataContract            lt  summary gt           lt typeparam name  T  gt The type of object being copied  lt  typeparam gt           lt param name  source  gt The object instance to copy  lt  param gt           lt returns gt The copied object  lt  returns gt      public static T CloneUsingDataContracts lt T gt  T source                if  IsDataContract typeof T      false                        throw new ArgumentException  The type must be a data contract     source                             Don t serialize a null object  simply return the default for that object         if  Object ReferenceEquals source  null                         return default T                      DataContractSerializer dcs   new DataContractSerializer typeof T            using Stream stream   new MemoryStream                          using  XmlDictionaryWriter writer   XmlDictionaryWriter CreateBinaryWriter stream                                 dcs WriteObject writer  source                   writer Flush                    stream Seek 0  SeekOrigin Begin                   using  XmlDictionaryReader reader   XmlDictionaryReader CreateBinaryReader stream  XmlDictionaryReaderQuotas Max                                         return  T dcs ReadObject reader                                                              lt summary gt          Helper function to check if a class is a  DataContract           lt  summary gt           lt param name  type  gt The type of the object to check  lt  param gt           lt returns gt Boolean flag indicating if the class is a DataContract  true  or not  false   lt  returns gt      public static bool IsDataContract Type type                object   attributes   type GetCustomAttributes typeof DataContractAttribute   false           return attributes Length    1

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Follow these steps    Define an ISelf lt T gt  with a read-only Self property that returns T  and ICloneable lt out T gt   which derives from ISelf lt T gt  and includes a method T Clone    Then define a CloneBase type which implements a protected virtual generic VirtualClone casting MemberwiseClone to the passed-in type    Each derived type should implement VirtualClone by calling the base clone method and then doing whatever needs to be done to properly clone those aspects of the derived type which the parent VirtualClone method hasn t yet handled    For maximum inheritance versatility  classes exposing public cloning functionality should be sealed  but derive from a base class which is otherwise identical except for the lack of cloning   Rather than passing variables of the explicit clonable type  take a parameter of type ICloneable lt theNonCloneableType gt    This will allow a routine that expects a cloneable derivative of  Foo to work with a cloneable derivative of DerivedFoo  but also allow the creation of non-cloneable derivatives of Foo

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For the cloning process  the object can be converted to the byte array first and then converted back to the object   public static class Extentions       public static T Clone lt T gt  this T obj                byte   buffer   BinarySerialize obj           return  T BinaryDeserialize buffer              public static byte   BinarySerialize object obj                using  var stream   new MemoryStream                          var formatter   new BinaryFormatter                 formatter Serialize stream  obj                return stream ToArray                         public static object BinaryDeserialize byte   buffer                using  var stream   new MemoryStream buffer                        var formatter   new BinaryFormatter                return formatter Deserialize stream                       The object must be serialized for the serialization process    Serializable  public class MyObject       public string Name    get  set        Usage   MyObject myObj    GetMyObj    MyObject newObj   myObj Clone

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I came up with this to overcome a  NET shortcoming having to manually deep copy List lt T    I use this   static public IEnumerable lt SpotPlacement gt  CloneList List lt SpotPlacement gt  spotPlacements        foreach  SpotPlacement sp in spotPlacements                yield return  SpotPlacement sp Clone              And at another place   public object Clone         OrderItem newOrderItem   new OrderItem                newOrderItem  exactPlacements AddRange SpotPlacement CloneList  exactPlacements                return newOrderItem      I tried to come up with oneliner that does this  but it s not possible  due to yield not working inside anonymous method blocks   Better still  use generic List lt T  cloner   class Utility lt T gt  where T   ICloneable       static public IEnumerable lt T gt  CloneList List lt T gt  tl                foreach  T t in tl                        yield return  T t Clone

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I found a new way to do it that is Emit   We can use Emit to add the IL to app and run it  But I dont think its a good way for I want to perfect this that I write my answer   The Emit can see the official document and Guide  You should learn some IL to read the code  I will write the code that can copy the property in class   public static class Clone                  ReSharper disable once InconsistentNaming     public static void CloneObjectWithIL lt T gt  T source  T los                  see http   lindexi oschina io lindexi post C- E4 BD BF E7 94 A8Emit E6 B7 B1 E5 85 8B E9 9A 86          if  CachedIl ContainsKey typeof T                            Action lt T  T gt   CachedIl typeof T    source  los               return                    var dynamicMethod   new DynamicMethod  Clone   null  new     typeof T   typeof T              ILGenerator generator   dynamicMethod GetILGenerator             foreach  var temp in typeof T  GetProperties   Where temp   gt  temp CanRead  amp  amp  temp CanWrite                           do not copy static that will except             if  temp GetAccessors true  0  IsStatic                                continue                             generator Emit OpCodes Ldarg 1     los             generator Emit OpCodes Ldarg 0     s             generator Emit OpCodes Callvirt  temp GetMethod               generator Emit OpCodes Callvirt  temp SetMethod                     generator Emit OpCodes Ret           var clone    Action lt T  T gt   dynamicMethod CreateDelegate typeof Action lt T  T gt             CachedIl typeof T     clone          clone source  los              private static Dictionary lt Type  Delegate gt  CachedIl   set  get      new Dictionary lt Type  Delegate gt         The code can be deep copy but it can copy the property  If you want to make it to deep copy that you can change it for the IL is too hard that I cant do it

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I prefer a copy constructor to a clone  The intent is clearer

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I think you can try this   MyObject myObj   GetMyObj       Create and fill a new object MyObject newObj   new MyObject myObj     DeepClone it

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A mapper performs a deep-copy  Foreach member of your object it creates a new object and assign all of its values  It works recursively on each non-primitive inner member   I suggest you one of the fastest  currently actively developed ones  I suggest UltraMapper https   github com maurosampietro UltraMapper  Nuget packages  https   www nuget org packages UltraMapper

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EDIT  project is discontinued  If you want true cloning to unknown types you can take a look at fastclone   That s expression based cloning working about 10 times faster than binary serialization and maintaining complete object graph integrity   That means  if you refer multiple times to the same object in your hierachy  the clone will also have a single instance beeing referenced   There is no need for interfaces  attributes or any other modification to the objects being cloned

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When using Marc Gravells protobuf-net as your serializer the accepted answer needs some slight modifications  as the object to copy won t be attributed with  Serializable  and  therefore  isn t serializable and the Clone-method will throw an exception  I modified it to work with protobuf-net   public static T Clone lt T gt  this T source        if Attribute GetCustomAttribute typeof T   typeof ProtoBuf ProtoContractAttribute                 null                throw new ArgumentException  Type has no ProtoContract     source               if Object ReferenceEquals source  null                 return default T              IFormatter formatter   ProtoBuf Serializer CreateFormatter lt T gt         using  Stream stream   new MemoryStream                  formatter Serialize stream  source           stream Seek 0  SeekOrigin Begin           return  T formatter Deserialize stream             This checks for the presence of a  ProtoContract  attribute and uses protobufs own formatter to serialize the object

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The generic approaches are all technically valid  but I just wanted to add a note from myself since we rarely actually need a real deep copy  and I would strongly oppose using generic deep copying in actual business applications since that makes it so you might have many places where the objects are copied and then modified explicitly  its easy to get lost    In most real-life situations also you want to have as much granular control over the copying process as possible since you are not only coupled to the data access framework but also in practice the copied business objects should rarely be 100  the same  Think an example  referenceId s used by the ORM to identify object references  a full deep copy will also copy this id s so while in-memory the objects will be different  as soon as you submit it to the datastore  it will complain  so you will have to modify this properties manually after copying anyway and if the object changes you need to adjust it in all of the places which use the generic deep copying   Expanding on  cregox answer with ICloneable  what actually is a deep copy  Its just a newly allocated object on the heap that is identical to the original object but occupies a different memory space  as such rather than using a generic cloner functionality why not just create a new object   I personally use the idea of static factory methods on my domain objects   Example       public class Client               public string Name   get  set             protected Client                                public static Client Clone Client copiedClient                        return new Client                               Name   copiedClient Name                                     public class Shop               public string Name   get  set             public string Address   get  set             public ICollection lt Client gt  Clients   get  set             public static Shop Clone Shop copiedShop  string newAddress  ICollection lt Client gt  clients                        var copiedClients   new List lt Client gt                 foreach  var client in copiedShop Clients                                copiedClients Add Client Clone client                               return new Shop                               Name   copiedShop Name                  Address   newAddress                  Clients   copiedClients                                  If someone is looking how he can structure object instantiation while retaining full control over the copying process that s a solution that I have been personally very successful with  The protected constructors also make it so  other developers are forced to use the factory methods which gives a neat single point of object instantiation encapsulating the construction logic inside of the object  You can also overload the method and have several clone logic s for different places if necessary

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The short answer is you inherit from the ICloneable interface and then implement the  clone function  Clone should do a memberwise copy and perform a deep copy on any member that requires it  then return the resulting object  This is a recursive operation   it requires that all members of the class you want to clone are either value types or implement ICloneable and that their members are either value types or implement ICloneable  and so on    For a more detailed explanation on Cloning using ICloneable  check out this article   The long answer is  it depends   As mentioned by others  ICloneable is not supported by generics  requires special considerations for circular class references  and is actually viewed by some as a  mistake  in the  NET Framework  The serialization method depends on your objects being serializable  which they may not be and you may have no control over  There is still much debate in the community over which is the  best  practice  In reality  none of the solutions are the one-size fits all best practice for all situations like ICloneable was originally interpreted to be   See the this Developer s Corner article for a few more options  credit to Ian

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Deep cloning is about copying state  For  net state means fields   Let s say one have an hierarchy   static class RandomHelper       private static readonly Random random   new Random         public static int Next int maxValue    gt  random Next maxValue      class A       private readonly int random   RandomHelper Next 100        public override string ToString     gt     typeof A  Name   nameof random      random       class B   A       private readonly int random   RandomHelper Next 100        public override string ToString     gt     typeof B  Name   nameof random      random   base ToString         class C   B       private readonly int random   RandomHelper Next 100        public override string ToString     gt     typeof C  Name   nameof random      random   base ToString          Cloning can be done   static class DeepCloneExtension          consider instance fields  both public and non-public     private static readonly BindingFlags bindingFlags           BindingFlags Public   BindingFlags NonPublic   BindingFlags Instance       public static T DeepClone lt T gt  this T obj  where T   new                 var type   obj GetType            var result    T Activator CreateInstance type            do                copy all fields             foreach  var field in type GetFields bindingFlags                   field SetValue result  field GetValue obj               for every level of hierarchy         while   type   type BaseType     typeof object             return result            Demo1   Console WriteLine new C     Console WriteLine new C      var c   new C    Console WriteLine    Environment NewLine Image   c  Environment NewLine      Console WriteLine new C     Console WriteLine new C      Console WriteLine    Environment NewLine Clone   c DeepClone    Environment NewLine      Console WriteLine new C     Console WriteLine new C       Result   C random   92 B random   66 A random   71 C random   36 B random   64 A random   17  Image  C random   96 B random   18 A random   46  C random   60 B random   7 A random   37 C random   78 B random   11 A random   18  Clone  C random   96 B random   18 A random   46  C random   33 B random   63 A random   38 C random   4 B random   5 A random   79   Notice  all new objects have random values for random field  but clone exactly matches the image  Demo2   class D       public event EventHandler Event      public void RaiseEvent     gt  Event  Invoke this  EventArgs Empty              var image   new D    Console WriteLine   Created obj   image GetHashCode        image Event     sender  e    gt  Console WriteLine   Event from obj   sender GetHashCode       Console WriteLine   Subscribed to event of obj   image GetHashCode        image RaiseEvent    image RaiseEvent     var clone   image DeepClone    Console WriteLine   obj   image GetHashCode    cloned to obj   clone GetHashCode        clone RaiseEvent    image RaiseEvent      Result   Created obj  46104728 Subscribed to event of obj  46104728 Event from obj  46104728 Event from obj  46104728 obj  46104728 cloned to obj  12289376 Event from obj  12289376 Event from obj  46104728   Notice  event backing field is copied too and client is subscribed to clone s event too

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The best is to implement an extension method like  public static T DeepClone lt T gt  this T originalObject       the cloning code        and then use it anywhere in the solution by  var copy   anyObject DeepClone      We can have the following three implementations    By Serialization  the shortest code  By Reflection - 5x faster By Expression Trees - 20x faster   All linked methods are well working and were deeply tested

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I prefer a copy constructor to a clone  The intent is clearer

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It s unbelievable how much effort you can spend with IClonable interface - especially if you have heavy class hierarchies  Also MemberwiseClone works somehow oddly - it does not exactly clone even normal List type kind of structures   And of course most interesting dilemma for serialization is to serialize back references - e g  class hierarchies where you have child-parent relationships  I doubt that binary serializer will be able to help you in this case   It will end up with recursive loops   stack overflow    I somehow liked solution proposed here  How do you do a deep copy of an object in  NET  C  specifically    however - it did not support Lists  added that support  also took into account re-parenting   For parenting only rule which I have made that field or property should be named  parent   then it will be ignored by DeepClone  You might want to decide your own rules for back-references - for tree hierarchies it might be  left right   etc     Here is whole code snippet including test code    using System  using System Collections  using System Collections Generic  using System Diagnostics  using System Linq  using System Reflection  using System Text   namespace TestDeepClone       class Program               static void Main string   args                        A a   new A                a name    main A               a b list Add new B a    name    b1                  a b list Add new B a    name    b2                   A a2    A a DeepClone                a2 name    second A                   Perform re-parenting manually after deep copy              foreach  var b in a2 b list                   b parent   a2                Debug WriteLine  ok                          public class A               public String name    one           public List lt String gt  list   new List lt string gt             public List lt String gt  null list          public List lt B gt  b list   new List lt B gt             private int private pleaseCopyMeAsWell   5           public override string ToString                         return  A     name                             public class B               public B               public B A  parent    parent    parent            public A parent          public String name    two               public static class ReflectionEx               public static Type GetUnderlyingType this MemberInfo member                        Type type              switch  member MemberType                                case MemberTypes Field                      type     FieldInfo member  FieldType                      break                  case MemberTypes Property                      type     PropertyInfo member  PropertyType                      break                  case MemberTypes Event                      type     EventInfo member  EventHandlerType                      break                  default                      throw new ArgumentException  member must be if type FieldInfo  PropertyInfo or EventInfo    member                              return Nullable GetUnderlyingType type     type                          lt summary gt              Gets fields and properties into one array              Order of properties   fields will be preserved in order of appearance in class   struct   MetadataToken is used for sorting such cases               lt  summary gt               lt param name  type  gt Type from which to get lt  param gt               lt returns gt array of fields and properties lt  returns gt          public static MemberInfo   GetFieldsAndProperties this Type type                        List lt MemberInfo gt  fps   new List lt MemberInfo gt                 fps AddRange type GetFields                 fps AddRange type GetProperties                 fps   fps OrderBy x   gt  x MetadataToken  ToList                return fps ToArray                       public static object GetValue this MemberInfo member  object target                        if  member is PropertyInfo                                return  member as PropertyInfo  GetValue target  null                             else if  member is FieldInfo                                return  member as FieldInfo  GetValue target                             else                               throw new Exception  member must be either PropertyInfo or FieldInfo                                     public static void SetValue this MemberInfo member  object target  object value                        if  member is PropertyInfo                                 member as PropertyInfo  SetValue target  value  null                             else if  member is FieldInfo                                 member as FieldInfo  SetValue target  value                             else                               throw new Exception  destinationMember must be either PropertyInfo or FieldInfo                                          lt summary gt              Deep clones specific object              Analogue can be found here  https   stackoverflow com questions 129389 how-do-you-do-a-deep-copy-an-object-in-net-c-specifically             This is now improved version  list support added               lt  summary gt               lt param name  obj  gt object to be cloned lt  param gt               lt returns gt full copy of object  lt  returns gt          public static object DeepClone this object obj                        if  obj    null                  return null               Type type   obj GetType                 if  obj is IList                                IList list     IList obj                   IList newlist    IList Activator CreateInstance obj GetType    list Count                    foreach  object elem in list                      newlist Add DeepClone elem                     return newlist                  if              if  type IsValueType    type    typeof string                                 return obj                            else if  type IsArray                                Type elementType   Type GetType type FullName Replace       string Empty                    var array   obj as Array                  Array copied   Array CreateInstance elementType  array Length                    for  int i   0  i  lt  array Length  i                        copied SetValue DeepClone array GetValue i    i                    return Convert ChangeType copied  obj GetType                               else if  type IsClass                                object toret   Activator CreateInstance obj GetType                      MemberInfo   fields   type GetFieldsAndProperties                    foreach  MemberInfo field in fields                                           Don t clone parent back-reference classes   Using special kind of naming  parent                          to indicate child s parent class                      if  field Name     parent                                                 continue                                             object fieldValue   field GetValue obj                        if  fieldValue    null                          continue                       field SetValue toret  DeepClone fieldValue                                       return toret                            else                                  Don t know that type  don t know how to clone it                  if  Debugger IsAttached                      Debugger Break                     return null                            DeepClone

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Well I was having problems using ICloneable in Silverlight  but I liked the idea of seralization  I can seralize XML  so I did this   static public class SerializeHelper         Michael White  Holly Springs Consulting  2009       michael hollyspringsconsulting com     public static T DeserializeXML lt T gt  string xmlData  where T new                 if  string IsNullOrEmpty xmlData               return default T            TextReader tr   new StringReader xmlData           T DocItms   new T            XmlSerializer xms   new XmlSerializer DocItms GetType             DocItms    T xms Deserialize tr            return DocItms    null   default T    DocItms             public static string SeralizeObjectToXML lt T gt  T xmlObject                StringBuilder sbTR   new StringBuilder            XmlSerializer xmsTR   new XmlSerializer xmlObject GetType             XmlWriterSettings xwsTR   new XmlWriterSettings             XmlWriter xmwTR   XmlWriter Create sbTR  xwsTR           xmsTR Serialize xmwTR xmlObject            return sbTR ToString               public static T CloneObject lt T gt  T objClone  where T new                 string GetString   SerializeHelper SeralizeObjectToXML lt T gt  objClone           return SerializeHelper DeserializeXML lt T gt  GetString

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The short answer is you inherit from the ICloneable interface and then implement the  clone function  Clone should do a memberwise copy and perform a deep copy on any member that requires it  then return the resulting object  This is a recursive operation   it requires that all members of the class you want to clone are either value types or implement ICloneable and that their members are either value types or implement ICloneable  and so on    For a more detailed explanation on Cloning using ICloneable  check out this article   The long answer is  it depends   As mentioned by others  ICloneable is not supported by generics  requires special considerations for circular class references  and is actually viewed by some as a  mistake  in the  NET Framework  The serialization method depends on your objects being serializable  which they may not be and you may have no control over  There is still much debate in the community over which is the  best  practice  In reality  none of the solutions are the one-size fits all best practice for all situations like ICloneable was originally interpreted to be   See the this Developer s Corner article for a few more options  credit to Ian

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A mapper performs a deep-copy  Foreach member of your object it creates a new object and assign all of its values  It works recursively on each non-primitive inner member   I suggest you one of the fastest  currently actively developed ones  I suggest UltraMapper https   github com maurosampietro UltraMapper  Nuget packages  https   www nuget org packages UltraMapper

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To clone your class object you can use the Object MemberwiseClone method   just add this function to your class    public class yourClass                              public yourClass DeepCopy                 yourClass othercopy    yourClass this MemberwiseClone            return othercopy            then to perform a deep independant copy  just call the DeepCopy method    yourClass newLine   oldLine DeepCopy      hope this helps

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how about just recasting inside a method  that should invoke basically a automatic copy constructor  T t   new T    T t2    T t     eh something like that          List lt myclass gt  cloneum          public void SomeFuncB ref List lt myclass gt   mylist                        cloneum   new List lt myclass gt                 cloneum    List  lt  myclass  gt    mylist              cloneum Add new myclass 3                 mylist   new List lt myclass gt                 seems to work to me

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I ve just created CloneExtensions library project  It performs fast  deep clone using simple assignment operations generated by Expression Tree runtime code compilation   How to use it   Instead of writing your own Clone or Copy methods with a tone of assignments between fields and properties make the program do it for yourself  using Expression Tree  GetClone lt T gt    method marked as extension method allows you to simply call it on your instance   var newInstance   source GetClone      You can choose what should be copied from source to newInstance using CloningFlags enum   var newInstance        source GetClone CloningFlags Properties   CloningFlags CollectionItems     What can be cloned    Primitive  int  uint  byte  double  char  etc    known immutable types  DateTime  TimeSpan  String  and delegates  including Action  Func  etc  Nullable T   arrays Custom classes and structs  including generic classes and structs    Following class struct members are cloned internally    Values of public  not readonly fields Values of public properties with both get and set accessors Collection items for types implementing ICollection   How fast it is   The solution is faster then reflection  because members information has to be gathered only once  before GetClone lt T gt  is used for the first time for given type T   It s also faster than serialization-based solution when you clone more then couple instances of the same type T   and more     Read more about generated expressions on documentation   Sample expression debug listing for List lt int gt     Lambda  Lambda1 lt System Func 4 System Collections Generic List 1 System Int32  CloneExtensions CloningFlags System Collections Generic IDictionary 2 System Type System Func 2 System Object System Object   System Collections Generic List 1 System Int32   gt       System Collections Generic List 1 System Int32   source      CloneExtensions CloningFlags  flags      System Collections Generic IDictionary 2 System Type System Func 2 System Object System Object    initializers         Block System Collections Generic List 1 System Int32   target             If   source    null                 Return  Label1   null              Else                Default System Void                      If                Call  initializers ContainsKey  Constant lt System Type gt  System Collections Generic List 1 System Int32                             target    System Collections Generic List 1 System Int32   Call   initializers Item  Constant lt System Type gt  System Collections Generic List 1 System Int32                  Invoke  System Object  source             Else                target    New System Collections Generic List 1 System Int32                        If                 System Byte  flags  amp   System Byte  Constant lt CloneExtensions CloningFlags gt  Fields       System Byte  Constant lt CloneExtensions CloningFlags gt  Fields                           Default System Void             Else                Default System Void                      If                 System Byte  flags  amp   System Byte  Constant lt CloneExtensions CloningFlags gt  Properties       System Byte  Constant lt CloneExtensions CloningFlags gt  Properties                           Block                      target Capacity    Call CloneExtensions CloneFactory GetClone                       source Capacity                       flags                       initializers                           Else                Default System Void                      If                 System Byte  flags  amp   System Byte  Constant lt CloneExtensions CloningFlags gt  CollectionItems       System Byte  Constant lt CloneExtensions CloningFlags gt  CollectionItems                           Block                  System Collections Generic IEnumerator 1 System Int32   var1                  System Collections Generic ICollection 1 System Int32   var2                     var1    System Collections Generic IEnumerator 1 System Int32   Call  source GetEnumerator                     var2    System Collections Generic ICollection 1 System Int32   target                   Loop                         If   Call  var1 MoveNext      False                             Call  var2 Add  Call CloneExtensions CloneFactory GetClone                                   var1 Current                                   flags                              initializers                      Else                        Break  Label2                                                  LabelTarget  Label2                   Else            Default System Void              Label          target      LabelTarget  Label1         what has the same meaning like following c  code    source  flags  initializers    gt        if source    null          return null       if initializers ContainsKey typeof List lt int gt            target    List lt int gt  initializers typeof List lt int gt    Invoke  object source       else         target   new List lt int gt          if  flags  amp  CloningFlags Properties     CloningFlags Properties                target Capacity   target Capacity GetClone flags  initializers              if  flags  amp  CloningFlags CollectionItems     CloningFlags CollectionItems                var targetCollection    ICollection lt int gt  target          foreach var item in  ICollection lt int gt  source                        targetCollection Add item Clone flags  initializers                         return target      Isn t it quite like how you d write your own Clone method for List lt int gt

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If you re already using a 3rd party application like ValueInjecter or Automapper  you can do something like this   MyObject oldObj     The existing object to clone  MyObject newObj   new MyObject    newObj InjectFrom oldObj      Using ValueInjecter syntax   Using this method you don t have to implement ISerializable or ICloneable on your objects  This is common with the MVC MVVM pattern  so simple tools like this have been created   see the ValueInjecter deep cloning sample on GitHub

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Basically you need to implement ICloneable interface and then realize object structure copying   If it s deep copy of all members  you need to insure  not relating on solution you choose  that all children are clonable as well   Sometimes you need to be aware of some restriction during this process  for example if you copying the ORM objects most of frameworks allow only one object attached to the session and you MUST NOT make clones of this object  or if it s possible you need to care about session attaching of these objects    Cheers

[c#] Deep cloning objects

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