Compare two objects properties to find differences

Question

I have two objects of the same type  and I want to loop through the public properties on each of them and alert the user about which properties don t match   Is it possible to do this without knowing what properties the object contains

User · Answer

Yes   Use Reflection   With Reflection  you can do things like     given object of some type object myObjectFromSomewhere  Type myObjOriginalType   myObjectFromSomewhere GetType    PropertyInfo   myProps   myObjOriginalType GetProperties      And then you can use the resulting PropertyInfo classes to compare all manner of things

User · Answer

Yes  with reflection - assuming each property type implements Equals appropriately  An alternative would be to use ReflectiveEquals recursively for all but some known types  but that gets tricky   public bool ReflectiveEquals object first  object second        if  first    null  amp  amp  second    null                return true            if  first    null    second    null                return false            Type firstType   first GetType        if  second GetType      firstType                return false     Or throw an exception              This will only use public properties  Is that enough      foreach  PropertyInfo propertyInfo in firstType GetProperties                  if  propertyInfo CanRead                        object firstValue   propertyInfo GetValue first  null               object secondValue   propertyInfo GetValue second  null               if   object Equals firstValue  secondValue                                 return false                                    return true

User · Answer

The real problem   How to get the difference of two sets    The fastest way I ve found is to convert the sets to dictionaries first  then diff  em   Here s  a generic approach   static IEnumerable lt T gt  DictionaryDiff lt K  T gt  Dictionary lt K  T gt  d1  Dictionary lt K  T gt  d2        return from x in d1 where  d2 ContainsKey x Key  select x Value      Then you can do something like this   static public IEnumerable lt PropertyInfo gt  PropertyDiff Type t1  Type t2        var d1   t1 GetProperties   ToDictionary x   gt  x Name       var d2   t2 GetProperties   ToDictionary x   gt  x Name       return DictionaryDiff d1  d2

User · Answer

As many mentioned the recursive approach  this is the function you can pass the searched name and the property to begin with to       public static void loopAttributes PropertyInfo prop  string targetAttribute  object tempObject                foreach  PropertyInfo nestedProp in prop PropertyType GetProperties                          if nestedProp Name    targetAttribute                                  found the matching attribute                           loopAttributes nestedProp  targetAttribute  prop GetValue tempObject                      in the main function foreach  PropertyInfo prop in rootObject GetType   GetProperties          loopAttributes prop  targetAttribute  rootObject

User · Answer

Type GetProperties will list each of the properties of a given type  Then use PropertyInfo GetValue to check the values

User · Answer

Comparing two objects of the same type using LINQ and Reflection  NB  This is basically a rewrite of the solution from Jon Skeet  but with a more compact and modern syntax  It should also generate slightly more effecticve IL   It goes something like this   public bool ReflectiveEquals LocalHdTicket serverTicket  LocalHdTicket localTicket           if  serverTicket    null  amp  amp  localTicket    null  return true       if  serverTicket    null    localTicket    null  return false        var firstType   serverTicket GetType            Handle type mismatch anyway you please       if localTicket GetType      firstType  throw new Exception  Trying to compare two different object types           return   from propertyInfo in firstType GetProperties                  where propertyInfo CanRead                let serverValue   propertyInfo GetValue serverTicket  null                 let localValue   propertyInfo GetValue localTicket  null                 where  Equals serverValue  localValue                 select serverValue  Any

User · Answer

Compare NET Objects can help you  CompareLogic logic   new CompareLogic    var compare   logic Compare obj1  obj2   comparacao Differences ForEach diff   gt  Debug Write diff PropertyName       Or formatted summary Debug Write comparacao DifferencesString

User · Answer

I know this is probably overkill  but here s my ObjectComparer class I use for this very purpose        lt summary gt      Utility class for comparing objects       lt  summary gt  public static class ObjectComparer            lt summary gt          Compares the public properties of any 2 objects and determines if the properties of each         all contain the same value           lt para gt           In cases where object1 and object2 are of different Types  both being derived from Type T           we will cast both objects down to the base Type T to ensure the property comparison is only          completed on COMMON properties           ex  Type T is Foo  object1 is GoodFoo and object2 is BadFoo -- both being inherited from Foo --         both objects will be cast to Foo for comparison           lt  para gt           lt  summary gt           lt typeparam name  T  gt Any class with public properties  lt  typeparam gt           lt param name  object1  gt Object to compare to object2  lt  param gt           lt param name  object2  gt Object to compare to object1  lt  param gt           lt param name  propertyInfoList  gt A List of  lt see cref  PropertyInfo   gt  objects that contain data on the properties         from object1 that are not equal to the corresponding properties of object2  lt  param gt           lt returns gt A boolean value indicating whether or not the properties of each object match  lt  returns gt      public static bool GetDifferentProperties lt T gt    T object1   T object2   out List lt PropertyInfo gt  propertyInfoList           where T   class               return GetDifferentProperties lt T gt   object1   object2   null   out propertyInfoList                    lt summary gt          Compares the public properties of any 2 objects and determines if the properties of each         all contain the same value           lt para gt           In cases where object1 and object2 are of different Types  both being derived from Type T           we will cast both objects down to the base Type T to ensure the property comparison is only          completed on COMMON properties           ex  Type T is Foo  object1 is GoodFoo and object2 is BadFoo -- both being inherited from Foo --         both objects will be cast to Foo for comparison           lt  para gt           lt  summary gt           lt typeparam name  T  gt Any class with public properties  lt  typeparam gt           lt param name  object1  gt Object to compare to object2  lt  param gt           lt param name  object2  gt Object to compare to object1  lt  param gt           lt param name  ignoredProperties  gt A list of  lt see cref  PropertyInfo   gt  objects         to ignore when completing the comparison  lt  param gt           lt param name  propertyInfoList  gt A List of  lt see cref  PropertyInfo   gt  objects that contain data on the properties         from object1 that are not equal to the corresponding properties of object2  lt  param gt           lt returns gt A boolean value indicating whether or not the properties of each object match  lt  returns gt      public static bool GetDifferentProperties lt T gt    T object1   T object2   List lt PropertyInfo gt  ignoredProperties   out List lt PropertyInfo gt  propertyInfoList           where T   class               propertyInfoList   new List lt PropertyInfo gt                 If either object is null  we can t compare anything         if   object1    null    object2    null                         return false                     Type object1Type   object1 GetType            Type object2Type   object2 GetType                In cases where object1 and object2 are of different Types  both being derived from Type T              we will cast both objects down to the base Type T to ensure the property comparison is only             completed on COMMON properties              ex  Type T is Foo  object1 is GoodFoo and object2 is BadFoo -- both being inherited from Foo --            both objects will be cast to Foo for comparison          if   object1Type    object2Type                         object1Type   typeof   T                object2Type   typeof   T                          Remove any properties to be ignored         List lt PropertyInfo gt  comparisonProps               RemoveProperties  object1Type GetProperties     ignoredProperties             foreach   PropertyInfo object1Prop in comparisonProps                         Type propertyType   null              object object1PropValue   null              object object2PropValue   null                  Rule out an attempt to check against a property which requires                an index  such as one accessed via this               if   object1Prop GetIndexParameters   GetLength  0      0                                    Get the value of each property                 object1PropValue   object1Prop GetValue  object1   null                    object2PropValue   object2Type GetProperty  object1Prop Name   GetValue  object2   null                        As we are comparing 2 objects of the same type we know                    that they both have the same properties  so grab the                    first non-null value                 if   object1PropValue    null                       propertyType   object1PropValue GetType   GetInterface   IComparable                      if   propertyType    null                       if   object2PropValue    null                           propertyType   object2PropValue GetType   GetInterface   IComparable                                   If both objects have null values or were indexed properties  don t continue             if   propertyType    null                                    If one property value is null and the other is not null                      they aren t equal  this is done here as a native CompareTo                    won t work with a null value as the target                 if   object1PropValue    null    object2PropValue    null                                         propertyInfoList Add  object1Prop                                      else                                          Use the native CompareTo method                     MethodInfo nativeCompare   propertyType GetMethod   CompareTo                             Sanity Check                         If we don t have a native CompareTo OR both values are null  we can t compare                         hence  we can t confirm the values differ    just go to the next property                     if   nativeCompare    null                                                    Return the native CompareTo result                         bool equal     0     int    nativeCompare Invoke  object1PropValue   new object    object2PropValue                                  if    equal                                                         propertyInfoList Add  object1Prop                                                                                                      return propertyInfoList Count    0                  lt summary gt          Compares the public properties of any 2 objects and determines if the properties of each         all contain the same value           lt para gt           In cases where object1 and object2 are of different Types  both being derived from Type T           we will cast both objects down to the base Type T to ensure the property comparison is only          completed on COMMON properties           ex  Type T is Foo  object1 is GoodFoo and object2 is BadFoo -- both being inherited from Foo --         both objects will be cast to Foo for comparison           lt  para gt           lt  summary gt           lt typeparam name  T  gt Any class with public properties  lt  typeparam gt           lt param name  object1  gt Object to compare to object2  lt  param gt           lt param name  object2  gt Object to compare to object1  lt  param gt           lt returns gt A boolean value indicating whether or not the properties of each object match  lt  returns gt      public static bool HasSamePropertyValues lt T gt    T object1   T object2           where T   class               return HasSamePropertyValues lt T gt   object1   object2   null                    lt summary gt          Compares the public properties of any 2 objects and determines if the properties of each         all contain the same value           lt para gt           In cases where object1 and object2 are of different Types  both being derived from Type T           we will cast both objects down to the base Type T to ensure the property comparison is only          completed on COMMON properties           ex  Type T is Foo  object1 is GoodFoo and object2 is BadFoo -- both being inherited from Foo --         both objects will be cast to Foo for comparison           lt  para gt           lt  summary gt           lt typeparam name  T  gt Any class with public properties  lt  typeparam gt           lt param name  object1  gt Object to compare to object2  lt  param gt           lt param name  object2  gt Object to compare to object1  lt  param gt           lt param name  ignoredProperties  gt A list of  lt see cref  PropertyInfo   gt  objects         to ignore when completing the comparison  lt  param gt           lt returns gt A boolean value indicating whether or not the properties of each object match  lt  returns gt      public static bool HasSamePropertyValues lt T gt    T object1   T object2   List lt PropertyInfo gt  ignoredProperties           where T   class                   If either object is null  we can t compare anything         if   object1    null    object2    null                         return false                     Type object1Type   object1 GetType            Type object2Type   object2 GetType                In cases where object1 and object2 are of different Types  both being derived from Type T              we will cast both objects down to the base Type T to ensure the property comparison is only             completed on COMMON properties              ex  Type T is Foo  object1 is GoodFoo and object2 is BadFoo -- both being inherited from Foo --            both objects will be cast to Foo for comparison          if   object1Type    object2Type                         object1Type   typeof   T                object2Type   typeof   T                          Remove any properties to be ignored         List lt PropertyInfo gt  comparisonProps               RemoveProperties  object1Type GetProperties     ignoredProperties             foreach   PropertyInfo object1Prop in comparisonProps                         Type propertyType   null              object object1PropValue   null              object object2PropValue   null                  Rule out an attempt to check against a property which requires                an index  such as one accessed via this               if   object1Prop GetIndexParameters   GetLength  0      0                                    Get the value of each property                 object1PropValue   object1Prop GetValue  object1   null                    object2PropValue   object2Type GetProperty  object1Prop Name   GetValue  object2   null                        As we are comparing 2 objects of the same type we know                    that they both have the same properties  so grab the                    first non-null value                 if   object1PropValue    null                       propertyType   object1PropValue GetType   GetInterface   IComparable                      if   propertyType    null                       if   object2PropValue    null                           propertyType   object2PropValue GetType   GetInterface   IComparable                                   If both objects have null values or were indexed properties  don t continue             if   propertyType    null                                    If one property value is null and the other is not null                      they aren t equal  this is done here as a native CompareTo                    won t work with a null value as the target                 if   object1PropValue    null    object2PropValue    null                                         return false                                        Use the native CompareTo method                 MethodInfo nativeCompare   propertyType GetMethod   CompareTo                         Sanity Check                     If we don t have a native CompareTo OR both values are null  we can t compare                     hence  we can t confirm the values differ    just go to the next property                 if   nativeCompare    null                                            Return the native CompareTo result                     bool equal     0     int    nativeCompare Invoke  object1PropValue   new object    object2PropValue                              if    equal                                                 return false                                                                          return true                  lt summary gt          Removes any  lt see cref  PropertyInfo   gt  object in the supplied List of          properties from the supplied Array of properties           lt  summary gt           lt param name  allProperties  gt Array containing master list of           lt see cref  PropertyInfo   gt  objects  lt  param gt           lt param name  propertiesToRemove  gt List of  lt see cref  PropertyInfo   gt  objects to         remove from the supplied array of properties  lt  param gt           lt returns gt A List of  lt see cref  PropertyInfo   gt  objects  lt  returns gt      private static List lt PropertyInfo gt  RemoveProperties           IEnumerable lt PropertyInfo gt  allProperties   IEnumerable lt PropertyInfo gt  propertiesToRemove                 List lt PropertyInfo gt  innerPropertyList   new List lt PropertyInfo gt                 Add all properties to a list for easy manipulation         foreach   PropertyInfo prop in allProperties                         innerPropertyList Add  prop                          Sanity check         if   propertiesToRemove    null                            Iterate through the properties to ignore and remove them from the list of                 all properties  if they exist             foreach   PropertyInfo ignoredProp in propertiesToRemove                                 if   innerPropertyList Contains  ignoredProp                                           innerPropertyList Remove  ignoredProp                                                       return innerPropertyList

User · Answer

Sure you can with reflection   Here is the code to grab the properties off of a given type   var info   typeof SomeType  GetProperties      If you can give more info on what you re comparing about the properties we can get together a basic diffing algorithmn   This code for intstance will diff on names  public bool AreDifferent Type t1  Type t2      var list1   t1 GetProperties   OrderBy x   gt  x Name  Select x   gt  x Name     var list2   t2 GetProperties   OrderBy x   gt  x Name  Select x   gt  x Name     return list1 SequenceEqual list2

[c#] Compare two objects' properties to find differences?

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