How to Clone Objects

Question

When I do the following   anything done to Person b modifies Person a  I thought doing this would clone Person b from Person a   I also have NO idea if changing Person a will change Person b after the linking  Due to my code right now  I can only see this in 1 direction    Person a   new Person     head    big   feet    small     Person b   a    b head    small     now a head    small  too      Now if I do this instead   Person a becomes completely separate    Person b   new Person     head   a head  feet   a feet      Now this fine and kinda makes sense when comparing this behaviour to other things in C   BUT  this could get very annoying with large objects      Is there a way to shortcut this at all    Such as    Person b   a Values

User · Answer

This code worked for me  It also takes a very small amount of time to execute      public static void CopyTo this object Source  object Destination                foreach  var pS in Source GetType   GetProperties                          foreach  var pT in Destination GetType   GetProperties                                  if  pT Name    pS Name  continue                   pT GetSetMethod    Invoke Destination  new object                     pS GetGetMethod   Invoke  Source  null                       break

User · Answer

It couldn t be simpler than this      public SomeClass Clone               var clonedJson   JsonConvert SerializeObject  this            return JsonConvert DeserializeObject lt SomeClass gt   clonedJson          Just serialize any object to a JSON string and then deserialize it   This will do a deep copy

User · Answer

a and b are just two references to the same Person object   They both essentially hold the address of the Person   There is a ICloneable interface  though relatively few classes support it   With this  you would write   Person b   a Clone      Then  b would be an entirely separate Person   You could also implement a copy constructor   public Person Person src                  There is no built-in way to copy all the fields   You can do it through reflection  but there would be a performance penalty

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public static T Clone lt T gt  T obj            DataContractSerializer dcSer   new  DataContractSerializer obj GetType           MemoryStream memoryStream   new MemoryStream           dcSer WriteObject memoryStream  obj         memoryStream Position   0         T newObject    T dcSer ReadObject memoryStream         return newObject

User · Answer

Painlessly   Using NClone library  Person a   new Person     head    big   feet    small     Person b   Clone ObjectGraph a

User · Answer

In my opinion  the best way to do this is by implementing your own Clone   method as shown below  class Person       public string head      public string feet          Downside  It has to be manually implemented for every class     public Person Clone                 return new Person     head   this head  feet   this feet             class Program       public static void Main string   args                Person a   new Person     head    quot bigAF quot   feet    quot smol quot             Person b   a Clone             b head    quot notEvenThatBigTBH quot            Console WriteLine   quot  a head    a feet  quot            Console WriteLine   quot  b head    b feet  quot             Output   bigAf  smol notEvenThatBigTBH  smol  b is totally independent to a  due to it not being a reference  but a clone  Hope I could help

User · Answer

What you are looking is for a Cloning  You will need to Implement IClonable and then do the Cloning   Example   class Person     ICloneable       public string head      public string feet         region ICloneable Members      public object Clone                 return this MemberwiseClone                endregion     Then You can simply call the Clone method to do a ShallowCopy  In this particular Case also a DeepCopy   Person a   new Person     head    big   feet    small     Person b    Person  a Clone        You can use the MemberwiseClone method of the Object class to do the cloning

User · Answer

I use AutoMapper for this  It works like this   Mapper CreateMap typeof Person   typeof Person    Mapper Map a  b     Now person a has all the properties of person b   As an aside  AutoMapper works for differing objects as well  For more information  check it out at http   automapper org  Update  I use this syntax now  simplistically - really the CreateMaps are in AutoMapper profiles    Mapper CreateMap lt Person  Person gt   Mapper Map a  b     Note that you don t have to do a CreateMap to map one object of the same type to another  but if you don t  AutoMapper will create a shallow copy  meaning to the lay man that if you change one object  the other changes also

User · Answer

This happens because  Person  is a class  so it is passed by reference  In the statement  b   a  you are just copying a reference to the one and only  Person  instance that you created with the keyword new   The easiest way to have the behavior that you are looking for is to use a  value type    Just change the Person declaration from  class Person   to  struct Person

User · Answer

MemberwiseClone is a good way to do a shallow copy as others have suggested  It is protected however  so if you want to use it without changing the class  you have to access it via reflection  Reflection however is slow  So if you are planning to clone a lot of objects it might be worthwhile to cache the result   public static class CloneUtil lt T gt        private static readonly Func lt T  object gt  clone       static CloneUtil                 var cloneMethod   typeof T  GetMethod  MemberwiseClone   System Reflection BindingFlags Instance   System Reflection BindingFlags NonPublic           clone    Func lt T  object gt  cloneMethod CreateDelegate typeof Func lt T  object gt                public static T ShallowClone T obj    gt   T clone obj      public static class CloneUtil       public static T ShallowClone lt T gt  this T obj    gt  CloneUtil lt T gt  ShallowClone obj       You can call it like this   Person b   a ShallowClone

User · Answer

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

User · Answer

Is there a way to shortcut this at all    No  not really   You ll need to make a new instance in order to avoid the original from affecting the  copy    There are a couple of options for this    If your type is a struct  not a class  it will be copied by value  instead of just copying the reference to the instance    This will give it the semantics you re describing  but has many other side effects that tend to be less than desirable  and is not recommended for any mutable type  which this obviously is  or this wouldn t be an issue   Implement a  cloning  mechanism on your types   This can be ICloneable or even just a constructor that takes an instance and copies values from it  Use reflection  MemberwiseClone  or similar to copy all values across  so you don t have to write the code to do this   This has potential problems  especially if you have fields containing non-simple types

User · Answer

Since the MemberwiseClone   method is not public  I created this simple extension method in order to make it easier to clone objects   public static T Clone lt T gt  this T obj        var inst   obj GetType   GetMethod  MemberwiseClone   System Reflection BindingFlags Instance   System Reflection BindingFlags NonPublic        return  T inst  Invoke obj  null       Usage   var clone   myObject Clone

User · Answer

You could do it like this   var jss   new JavaScriptSerializer    var b   jss Deserialize lt Person gt  jss Serialize a      For deep cloning you may want to take a look at this answer  https   stackoverflow com a 78612 550975

[c#] How to Clone Objects

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