Best way to compare two complex objects

Question

I have two complex objects like Object1 and Object2  They have around 5 levels of child objects   I need the fastest method to say if they are same or not   How could this be done in C  4 0

User · Answer

Thanks to the example of Jonathan  I expanded it for all cases  arrays  lists  dictionaries  primitive types    This is a comparison without serialization and does not require the implementation of any interfaces for compared objects                lt summary gt Returns description of difference or empty value if equal lt  summary gt          public static string Compare object obj1  object obj2  string path                             string path1   string IsNullOrEmpty path         path                     if  obj1    null  amp  amp  obj2    null                  return path1    null    not null               else if  obj2    null  amp  amp  obj1    null                  return path1    not null    null               else if  obj1    null  amp  amp  obj2    null                  return null               if   obj1 GetType   Equals obj2 GetType                     return  different types      obj1 GetType       and     obj2 GetType                 Type type   obj1 GetType                if  path                        path   type Name               if  type IsPrimitive    typeof string  Equals type                                 if   obj1 Equals obj2                       return path1         obj1              obj2                        return null                            if  type IsArray                                Array first   obj1 as Array                  Array second   obj2 as Array                  if  first Length    second Length                      return path1    array size differs      first Length     vs     second Length                         var en   first GetEnumerator                    int i   0                  while  en MoveNext                                          string res   Compare en Current  second GetValue i   path                       if  res    null                          return res      Index     i                            i                                                else if  typeof System Collections IEnumerable  IsAssignableFrom type                                 System Collections IEnumerable first   obj1 as System Collections IEnumerable                  System Collections IEnumerable second   obj2 as System Collections IEnumerable                   var en   first GetEnumerator                    var en2   second GetEnumerator                    int i   0                  while  en MoveNext                                          if   en2 MoveNext                            return path      enumerable size differs                        string res   Compare en Current  en2 Current  path                       if  res    null                          return res      Index     i                            i                                                else                               foreach  PropertyInfo pi in type GetProperties BindingFlags NonPublic   BindingFlags Instance   BindingFlags Public                                         try                                               var val   pi GetValue obj1                           var tval   pi GetValue obj2                           if  path EndsWith       pi Name                               return null                          var pathNew    path Length    0        path          pi Name                          string res   Compare val  tval  pathNew                           if  res    null                              return res                                            catch  TargetParameterCountException                                                  index property                                                         foreach  FieldInfo fi in type GetFields BindingFlags NonPublic   BindingFlags Instance   BindingFlags Public                                         var val   fi GetValue obj1                       var tval   fi GetValue obj2                       if  path EndsWith       fi Name                           return null                      var pathNew    path Length    0        path          fi Name                      string res   Compare val  tval  pathNew                       if  res    null                          return res                                              return null              For easy copying of the code created repository

User · Answer

I ll assume you are not referring to literally the same objects  Object1    Object2   You might be thinking about doing a memory comparison between the two  memcmp Object1  Object2  sizeof Object GetType      But that s not even real code in c      Because all of your data is probably created on the heap  the memory is not contiguous and you can t just compare the equality of two objects in an agnostic manner  You re going to have to compare each value  one at a time  in a custom way   Consider adding the IEquatable lt T gt  interface to your class  and define a custom Equals method for your type  Then  in that method  manual test each value  Add IEquatable lt T gt  again on enclosed types if you can and repeat the process   class Foo   IEquatable lt Foo gt      public bool Equals Foo other             check all the values        return false

User · Answer

Use IEquatable lt T gt  Interface which has a method Equals

User · Answer

Serialize both objects  then calculate Hash Code  then compare

User · Answer

public class GetObjectsComparison       public object FirstObject  SecondObject      public BindingFlags BindingFlagsConditions  BindingFlags Public   BindingFlags NonPublic   BindingFlags Instance   BindingFlags Static    public struct SetObjectsComparison       public FieldInfo SecondObjectFieldInfo      public dynamic FirstObjectFieldInfoValue  SecondObjectFieldInfoValue      public bool ErrorFound      public GetObjectsComparison GetObjectsComparison    private static bool ObjectsComparison GetObjectsComparison GetObjectsComparison        GetObjectsComparison FunctionGet   GetObjectsComparison      SetObjectsComparison FunctionSet   new SetObjectsComparison        if  FunctionSet ErrorFound  false          foreach  FieldInfo FirstObjectFieldInfo in FunctionGet FirstObject GetType   GetFields FunctionGet BindingFlagsConditions                         FunctionSet SecondObjectFieldInfo               FunctionGet SecondObject GetType   GetField FirstObjectFieldInfo Name  FunctionGet BindingFlagsConditions                FunctionSet FirstObjectFieldInfoValue   FirstObjectFieldInfo GetValue FunctionGet FirstObject               FunctionSet SecondObjectFieldInfoValue   FunctionSet SecondObjectFieldInfo GetValue FunctionGet SecondObject               if  FirstObjectFieldInfo FieldType IsNested                                FunctionSet GetObjectsComparison                   new GetObjectsComparison                                         FirstObject   FunctionSet FirstObjectFieldInfoValue                                           SecondObject   FunctionSet SecondObjectFieldInfoValue                                     if   ObjectsComparison FunctionSet GetObjectsComparison                                         FunctionSet ErrorFound   true                      break                                              else if  FunctionSet FirstObjectFieldInfoValue    FunctionSet SecondObjectFieldInfoValue                                FunctionSet ErrorFound   true                  break                              return  FunctionSet ErrorFound

User · Answer

Based off a few answers already given here I decided to mostly back JoelFan s answer   I love extension methods and these have been working great for me when none of the other solutions would using them to compare my complex classes   Extension Methods  using System IO  using System Xml Serialization   static class ObjectHelpers       public static string SerializeObject lt T gt  this T toSerialize                XmlSerializer xmlSerializer   new XmlSerializer toSerialize GetType              using  StringWriter textWriter   new StringWriter                          xmlSerializer Serialize textWriter  toSerialize               return textWriter ToString                         public static bool EqualTo this object obj  object toCompare                if  obj SerializeObject      toCompare SerializeObject                return true          else             return false             public static bool IsBlank lt T gt  this T obj  where T  new                 T blank   new T            T newObj     T obj            if  newObj SerializeObject      blank SerializeObject                return true          else             return false             Usage Examples  if  record IsBlank        throw new Exception  Record found is blank      if  record EqualTo new record         throw new Exception  Record found is blank

User · Answer

Serialize both objects and compare the resulting strings

User · Answer

Serialize both objects and compare the resulting strings by  JoelFan  So to do this  create a static class like so and use Extensions to extend ALL objects  so you can pass anytype of object  collection  etc into the method   using System  using System IO  using System Runtime Serialization Json  using System Text   public static class MySerializer       public static string Serialize this object obj                var serializer   new DataContractJsonSerializer obj GetType             using  var ms   new MemoryStream                          serializer WriteObject ms  obj               return Encoding Default GetString ms ToArray                         Once you reference this static class in any other file  you can do this   Person p   new Person   Firstname    Jason   LastName    Argonauts     Person p2   new Person   Firstname    Jason   LastName    Argonaut       assuming you have already created a class person  string personString   p Serialize    string person2String   p2 Serialize      Now you can simply use  Equals to compare them  I use this for checking if objects are in collections too  It works really well

User · Answer

You can now use json net   Just go on Nuget and install it   And you can do something like this       public bool Equals SamplesItem sampleToCompare                string myself   JsonConvert SerializeObject this           string other   JsonConvert SerializeObject sampleToCompare            return myself    other          You could perhaps make a extension method for object if you wanted to get fancier   Please note this only compares the public properties   And if you wanted to ignore a public property when you do the comparison you could use the  JsonIgnore  attribute

User · Answer

If you don t want to implement IEquatable  you can always use Reflection to compare all the properties  - if they re value type  just compare them  -if they are reference type  call the function recursively to compare its  inner  properties   I m not thinking about performace  but about simplicity  It depends  however on the exact design of your objects  It could get complicated depending on your objects shape  for example if there are cyclic dependencies between properties   There are  however  several solutions out there that you can use  like this one    Compare  NET objects   Another option is to serialize the object as text  for example using JSON NET  and comparing the serialization result   JSON NET can handle Cyclic dependencies between properties    I don t know if by fastest you mean the fastest way to implement it or a code that runs fast  You should not optimize before knowing if you need to  Premature optimization is the root of all evil

User · Answer

One way to do this would be to override Equals   on each type involved  For example  your top level object would override Equals   to call the Equals   method of all 5 child objects  Those objects should all override Equals   as well  assuming they are custom objects  and so on until the entire hierarchy could be compared by just performing an equality check on the top level objects

User · Answer

I would say that   Object1 Equals Object2   would be what you re looking for  That s if you re looking to see if the objects are the same  which is what you seem to be asking   If you want to check to see if all the child objects are the same  run them through a loop with the Equals   method

User · Answer

Implement IEquatable lt T gt   typically in conjunction with overriding the inherited Object Equals and Object GetHashCode methods  on all your custom types  In the case of composite types  invoke the contained types    Equals method within the containing types  For contained collections  use the SequenceEqual extension method  which internally calls IEquatable lt T gt  Equals or Object Equals on each element  This approach will obviously require you to extend your types    definitions  but its results are faster than any generic solutions involving serialization   Edit  Here is a contrived example with three levels of nesting    For value types  you can typically just call their Equals method  Even if the fields or properties were never explicitly assigned  they would still have a default value   For reference types  you should first call ReferenceEquals  which checks for reference equality     this would serve as an efficiency boost when you happen to be referencing the same object  It would also handle cases where both references are null  If that check fails  confirm that your instance s field or property is not null  to avoid NullReferenceException  and call its Equals method  Since our members are properly typed  the IEquatable lt T gt  Equals method gets called directly  bypassing the overridden Object Equals method  whose execution would be marginally slower due to the type cast    When you override Object Equals  you   re also expected to override Object GetHashCode  I didn   t do so below for the sake of conciseness   public class Person   IEquatable lt Person gt        public int Age   get  set        public string FirstName   get  set        public Address Address   get  set         public override bool Equals object obj                return this Equals obj as Person              public bool Equals Person other                if  other    null              return false           return this Age Equals other Age   amp  amp                                object ReferenceEquals this FirstName  other FirstName                     this FirstName    null  amp  amp                  this FirstName Equals other FirstName                 amp  amp                                object ReferenceEquals this Address  other Address                     this Address    null  amp  amp                  this Address Equals other Address                          public class Address   IEquatable lt Address gt        public int HouseNo   get  set        public string Street   get  set        public City City   get  set         public override bool Equals object obj                return this Equals obj as Address              public bool Equals Address other                if  other    null              return false           return this HouseNo Equals other HouseNo   amp  amp                                object ReferenceEquals this Street  other Street                     this Street    null  amp  amp                  this Street Equals other Street                 amp  amp                                object ReferenceEquals this City  other City                     this City    null  amp  amp                  this City Equals other City                          public class City   IEquatable lt City gt        public string Name   get  set         public override bool Equals object obj                return this Equals obj as City              public bool Equals City other                if  other    null              return false           return             object ReferenceEquals this Name  other Name                 this Name    null  amp  amp              this Name Equals other Name             Update  This answer was written several years ago  Since then  I ve started to lean away from implementing IEquality lt T gt  for mutable types for such scenarios  There are two notions of equality  identity and equivalence  At a memory representation level  these are popularly distinguished as    reference equality    and    value equality     see Equality Comparisons   However  the same distinction can also apply at a domain level  Suppose that your Person class has a PersonId property  unique per distinct real-world person  Should two objects with the same PersonId but different Age values be considered equal or different  The answer above assumes that one is after equivalence  However  there are many usages of the IEquality lt T gt  interface  such as collections  that assume that such implementations provide for identity  For example  if you re populating a HashSet lt T gt   you would typically expect a TryGetValue T T  call to return existing elements that share merely the identity of your argument  not necessarily equivalent elements whose contents are completely the same  This notion is enforced by the notes on GetHashCode      In general  for mutable reference types  you should override GetHashCode   only if          You can compute the hash code from fields that are not mutable  or   You can ensure that the hash code of a mutable object does not change while the object is contained in a collection that relies on its hash code

User · Answer

I found this below function for comparing objects    static bool Compare lt T gt  T Object1  T object2             Get the type of the object       Type type   typeof T            return false if any of the object is false       if  object Equals Object1  default T      object Equals object2  default T             return false          Loop through each properties inside class and get values for the property from both the objects and compare      foreach  System Reflection PropertyInfo property in type GetProperties                     if  property Name     ExtensionData                             string Object1Value   string Empty                string Object2Value   string Empty                if  type GetProperty property Name  GetValue Object1  null     null                      Object1Value   type GetProperty property Name  GetValue Object1  null  ToString                  if  type GetProperty property Name  GetValue object2  null     null                      Object2Value   type GetProperty property Name  GetValue object2  null  ToString                  if  Object1Value Trim      Object2Value Trim                                      return false                                          return true       I am using it and it is working fine for me

User · Answer

You can use extension method  recursion to resolve this problem   public static bool DeepCompare this object obj  object another           if  ReferenceEquals obj  another   return true    if   obj    null      another    null   return false      Compare two object s class  return false if they are difference   if  obj GetType      another GetType    return false     var result   true      Get all properties of obj     And compare each other   foreach  var property in obj GetType   GetProperties              var objValue   property GetValue obj         var anotherValue   property GetValue another         if   objValue Equals anotherValue   result   false         return result      public static bool CompareEx this object obj  object another     if  ReferenceEquals obj  another   return true   if   obj    null      another    null   return false   if  obj GetType      another GetType    return false      properties  int  double  DateTime  etc  not class  if   obj GetType   IsClass  return obj Equals another     var result   true   foreach  var property in obj GetType   GetProperties           var objValue   property GetValue obj       var anotherValue   property GetValue another         Recursion     if   objValue DeepCompare anotherValue     result   false      return result      or compare by using Json  if object is very complex  You can use Newtonsoft Json   public static bool JsonCompare this object obj  object another      if  ReferenceEquals obj  another   return true    if   obj    null      another    null   return false    if  obj GetType      another GetType    return false     var objJson   JsonConvert SerializeObject obj     var anotherJson   JsonConvert SerializeObject another      return objJson    anotherJson

[c#] Best way to compare two complex objects

Examples related to c#

Examples related to .net