Comparing object properties in c# [closed]

Question

This is what I've come up with as a method on a class inherited by many of my other classes. The idea is that it allows the simple comparison between properties of Objects of the same Type.

Now, this does work - but in the interest of improving the quality of my code I thought I'd throw it out for scrutiny. How can it be better/more efficient/etc.?

/// <summary>
/// Compare property values (as strings)
/// </summary>
/// <param name="obj"></param>
/// <returns></returns>
public bool PropertiesEqual(object comparisonObject)
{

    Type sourceType = this.GetType();
    Type destinationType = comparisonObject.GetType();

    if (sourceType == destinationType)
    {
        PropertyInfo[] sourceProperties = sourceType.GetProperties();
        foreach (PropertyInfo pi in sourceProperties)
        {
            if ((sourceType.GetProperty(pi.Name).GetValue(this, null) == null && destinationType.GetProperty(pi.Name).GetValue(comparisonObject, null) == null))
            {
                // if both are null, don't try to compare  (throws exception)
            }
            else if (!(sourceType.GetProperty(pi.Name).GetValue(this, null).ToString() == destinationType.GetProperty(pi.Name).GetValue(comparisonObject, null).ToString()))
            {
                // only need one property to be different to fail Equals.
                return false;
            }
        }
    }
    else
    {
        throw new ArgumentException("Comparison object must be of the same type.","comparisonObject");
    }

    return true;
}

Conveyance

See also: #3060882 and perhaps #987072 – Leonardoleoncavallo

By the way are you aware of this SE site: codereview.stackexchange.com – Xyster

There are a few object comparison libraries: CompareNETObjects, DeepEqual, AutoCompare, ZCompare ... – Bricklayer

...and a ton of generic equality comparer implementors, some of which are: MemberwiseEqualityComparer, Equ, SemanticComparison, EqualityComparer, DeepEqualityComparer, Equality, Equals.Fody. The latter group might be limited in scope and flexibility as to what they can achieve. – Bricklayer

I'm voting to close this question as off-topic because it belongs to code review – Sweepstakes

Answer 1

I was looking for a snippet of code that would do something similar to help with writing unit test. Here is what I ended up using.

public static bool PublicInstancePropertiesEqual<T>(T self, T to, params string[] ignore) where T : class 
  {
     if (self != null && to != null)
     {
        Type type = typeof(T);
        List<string> ignoreList = new List<string>(ignore);
        foreach (System.Reflection.PropertyInfo pi in type.GetProperties(System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance))
        {
           if (!ignoreList.Contains(pi.Name))
           {
              object selfValue = type.GetProperty(pi.Name).GetValue(self, null);
              object toValue = type.GetProperty(pi.Name).GetValue(to, null);

              if (selfValue != toValue && (selfValue == null || !selfValue.Equals(toValue)))
              {
                 return false;
              }
           }
        }
        return true;
     }
     return self == to;
  }

EDIT:

Same code as above but uses LINQ and Extension methods :

public static bool PublicInstancePropertiesEqual<T>(this T self, T to, params string[] ignore) where T : class
{
    if (self != null && to != null)
    {
        var type = typeof(T);
        var ignoreList = new List<string>(ignore);
        var unequalProperties =
            from pi in type.GetProperties(BindingFlags.Public | BindingFlags.Instance)
            where !ignoreList.Contains(pi.Name) && pi.GetUnderlyingType().IsSimpleType() && pi.GetIndexParameters().Length == 0
            let selfValue = type.GetProperty(pi.Name).GetValue(self, null)
            let toValue = type.GetProperty(pi.Name).GetValue(to, null)
            where selfValue != toValue && (selfValue == null || !selfValue.Equals(toValue))
            select selfValue;
        return !unequalProperties.Any();
    }
    return self == to;
}

public static class TypeExtensions
   {
      /// <summary>
      /// Determine whether a type is simple (String, Decimal, DateTime, etc) 
      /// or complex (i.e. custom class with public properties and methods).
      /// </summary>
      /// <see cref="https://mcmap.net/q/127380/-how-to-test-if-type-is-primitive"/>
      public static bool IsSimpleType(
         this Type type)
      {
         return
            type.IsValueType ||
            type.IsPrimitive ||
            new[]
            {
               typeof(String),
               typeof(Decimal),
               typeof(DateTime),
               typeof(DateTimeOffset),
               typeof(TimeSpan),
               typeof(Guid)
            }.Contains(type) ||
            (Convert.GetTypeCode(type) != TypeCode.Object);
      }

      public static Type GetUnderlyingType(this MemberInfo member)
      {
         switch (member.MemberType)
         {
            case MemberTypes.Event:
               return ((EventInfo)member).EventHandlerType;
            case MemberTypes.Field:
               return ((FieldInfo)member).FieldType;
            case MemberTypes.Method:
               return ((MethodInfo)member).ReturnType;
            case MemberTypes.Property:
               return ((PropertyInfo)member).PropertyType;
            default:
               throw new ArgumentException
               (
                  "Input MemberInfo must be if type EventInfo, FieldInfo, MethodInfo, or PropertyInfo"
               );
         }
      }
   }

Drawtube

Big T - quite an oldie, but definitely serves a great purpose for both testing and simple compares.. thanks +1 – Dayak

This is good, but I've found it not to work with more complex objects. For example I have an object with some strings (it compares them fine) but then this object also has a list of another object, which it doesn't compare correctly, so need to recurse this somehow. – Microdont

I had to add to criteria in the first where two more criteria because you have to exclude indexed properties which throw exception in other case. Here is the criteria for this error: pi.GetIndexParameters().Length == 0. And the second criteria to resolve the problem stated by @RyanThomas is this: pi.GetUnderlyingType().IsSimpleType(). As you will see, IsSimpleType is and extension that not exist for the class Type. I modified the answer to add all these conditions and the extension. – Balsamic

Answer 2

UPDATE: The latest version of Compare-Net-Objects is located on GitHub , has NuGet package and Tutorial. It can be called like

//This is the comparison class
CompareLogic compareLogic = new CompareLogic();

ComparisonResult result = compareLogic.Compare(person1, person2);

//These will be different, write out the differences
if (!result.AreEqual)
    Console.WriteLine(result.DifferencesString);

Or if you need to change some configuration, use

CompareLogic basicComparison = new CompareLogic() 
{ Config = new ComparisonConfig()
   { MaxDifferences = propertyCount 
     //add other configurations
   }
};

Full list of configurable parameters is in ComparisonConfig.cs

Original answer:

The limitations I see in your code:

• The biggest one is that it doesn't do a deep object comparison.

• It doesn't do an element by element comparison in case properties are lists or contain lists as elements (this can go n-levels).

• It doesn't take into account that some type of properties should not be compared (e.g. a Func property used for filtering purposes, like the one in the PagedCollectionView class).

• It doesn't keep track of what properties actually were different (so you can show in your assertions).

I was looking today for some solution for unit-testing purposes to do property by property deep comparison and I ended up using: http://comparenetobjects.codeplex.com.

It is a free library with just one class which you can simply use like this:

var compareObjects = new CompareObjects()
{
    CompareChildren = true, //this turns deep compare one, otherwise it's shallow
    CompareFields = false,
    CompareReadOnly = true,
    ComparePrivateFields = false,
    ComparePrivateProperties = false,
    CompareProperties = true,
    MaxDifferences = 1,
    ElementsToIgnore = new List<string>() { "Filter" }
};

Assert.IsTrue(
    compareObjects.Compare(objectA, objectB), 
    compareObjects.DifferencesString
);

Also, it can be easily re-compiled for Silverlight. Just copy the one class into a Silverlight project and remove one or two lines of code for comparisons that are not available in Silverlight, like private members comparison.

Scrivener

Liviu, I noticed your comment about the class not being compatible with Silverlight. I just changed it to be compatible with Silverlight and Windows Phone 7. Do a get latest. See change set 74131 at comparenetobjects.codeplex.com/SourceControl/list/changesets – Glabrescent

This looks promising. Gonna try it out – Cropper

Thank you for the great example! Also, IgnoreObjectTypes setting might be useful when there are different types. – Hourigan

Version 2.0 has a Portable Class Library version that is compatible with Silverlight 5+, Windows Phone 8+, WinRT 8+, Xamarin IOS and Xamarin Droid – Glabrescent

DifferencesString has been deprectated in the CompareObjects class. But now you can get that from the ComparisonResult instead: var r = compareObjects.Compare(objectA, objectB); Assert.IsTrue(r.AreEqual, r.DifferencesString); – Imperishable

Answer 3

I think it would be best to follow the pattern for Override Object#Equals()
For a better description: Read Bill Wagner's Effective C# - Item 9 I think

public override Equals(object obOther)
{
  if (null == obOther)
    return false;
  if (object.ReferenceEquals(this, obOther)
    return true;
  if (this.GetType() != obOther.GetType())
    return false;
  # private method to compare members.
  return CompareMembers(this, obOther as ThisClass);
}

• Also in methods that check for equality, you should return either true or false. either they are equal or they are not.. instead of throwing an exception, return false.
• I'd consider overriding Object#Equals.
• Even though you must have considered this, using Reflection to compare properties is supposedly slow (I dont have numbers to back this up). This is the default behavior for valueType#Equals in C# and it is recommended that you override Equals for value types and do a member wise compare for performance. (Earlier I speed-read this as you have a collection of custom Property objects... my bad.)

Update-Dec 2011:

• Of course, if the type already has a production Equals() then you need another approach.
• If you're using this to compare immutable data structures exclusively for test purposes, you shouldn't add an Equals to production classes (Someone might hose the tests by chainging the Equals implementation or you may prevent creation of a production-required Equals implementation).

Saracen

I ran into problems with overriding .Equals() because i'm trying to implement this on a base class that gets inherited... because I don't know the keys for the class this'll be run against, i can't implement a decent override for GetHasCode() (req'd when you override Equals()). – Conveyance

The requirement is that if objA.Equals(objB) then objA.GetHashCode() == objB.GetHashCode(). GetHashCode should not be dependent on mutable state/data of a class... I didnt get what you meant by keys for the class.. Seems like something that can be solved. Doesn't the base type have the 'keys'? – Saracen

Answer 4

If performance doesn't matter, you could serialize them and compare the results:

var serializer = new XmlSerializer(typeof(TheObjectType));
StringWriter serialized1 = new StringWriter(), serialized2 = new StringWriter();
serializer.Serialize(serialized1, obj1);
serializer.Serialize(serialized2, obj2);
bool areEqual = serialized1.ToString() == serialized2.ToString();

Cockup

tried this a whila ago, you would wonder how many objects are not serializable ... – Mcmanus

Answer 5

I think the answer of Big T was quite good but the deep comparison was missing, so I tweaked it a little bit:

using System.Collections.Generic;
using System.Reflection;

/// <summary>Comparison class.</summary>
public static class Compare
{
    /// <summary>Compare the public instance properties. Uses deep comparison.</summary>
    /// <param name="self">The reference object.</param>
    /// <param name="to">The object to compare.</param>
    /// <param name="ignore">Ignore property with name.</param>
    /// <typeparam name="T">Type of objects.</typeparam>
    /// <returns><see cref="bool">True</see> if both objects are equal, else <see cref="bool">false</see>.</returns>
    public static bool PublicInstancePropertiesEqual<T>(T self, T to, params string[] ignore) where T : class
    {
        if (self != null && to != null)
        {
            var type = self.GetType();
            var ignoreList = new List<string>(ignore);
            foreach (var pi in type.GetProperties(BindingFlags.Public | BindingFlags.Instance))
            {
                if (ignoreList.Contains(pi.Name))
                {
                    continue;
                }

                var selfValue = type.GetProperty(pi.Name).GetValue(self, null);
                var toValue = type.GetProperty(pi.Name).GetValue(to, null);

                if (pi.PropertyType.IsClass && !pi.PropertyType.Module.ScopeName.Equals("CommonLanguageRuntimeLibrary"))
                {
                    // Check of "CommonLanguageRuntimeLibrary" is needed because string is also a class
                    if (PublicInstancePropertiesEqual(selfValue, toValue, ignore))
                    {
                        continue;
                    }

                    return false;
                }

                if (selfValue != toValue && (selfValue == null || !selfValue.Equals(toValue)))
                {
                    return false;
                }
            }

            return true;
        }

        return self == to;
    }
}

Dejecta

Answer 6

I would add the following line to the PublicInstancePropertiesEqual method to avoid copy & paste errors:

Assert.AreNotSame(self, to);

Lightish

Answer 7

Do you override .ToString() on all of your objects that are in the properties? Otherwise, that second comparison could come back with null.

Also, in that second comparison, I'm on the fence about the construct of !( A == B) compared to (A != B), in terms of readability six months/two years from now. The line itself is pretty wide, which is ok if you've got a wide monitor, but might not print out very well. (nitpick)

Are all of your objects always using properties such that this code will work? Could there be some internal, non-propertied data that could be different from one object to another, but all exposed data is the same? I'm thinking of some data which could change over time, like two random number generators that happen to hit the same number at one point, but are going to produce two different sequences of information, or just any data that doesn't get exposed through the property interface.

Tims

good points - != ... agreed, point taken. ToString() was an attempt to workaround .GetValue returning an object (thus the comparison always false, as it's a ref compare).. is there a better way? – Conveyance

If GetValue is returning an object, can you recurse through this function again? ie, call PropertiesEqual on the returned objects? – Tims

Answer 8

Make sure objects aren't null.

Having obj1 and obj2:

if(obj1 == null )
{
   return false;
}
return obj1.Equals( obj2 );

Disarticulate

what if they're both null? aren't they then equal? – Tims

good point on nulls, in my case using .Equals() doesn't seem to work, which is why i've come up with this solution – Conveyance

well, the case i'm testing for is two objects, one newly created, one from the session. comparing the two with .Equals() returns false even though both have identical property values – Conveyance

Answer 9

If you are only comparing objects of the same type or further down the inheritance chain, why not specify the parameter as your base type, rather than object ?

Also do null checks on the parameter as well.

Furthermore I'd make use of 'var' just to make the code more readable (if its c#3 code)

Also, if the object has reference types as properties then you are just calling ToString() on them which doesn't really compare values. If ToString isn't overwridden then its just going to return the type name as a string which could return false-positives.

Befriend

good point on the reference types - in my case it doesn't matter but there's a good chance it would. – Conveyance

Answer 10

The first thing I would suggest would be to split up the actual comparison so that it's a bit more readable (I've also taken out the ToString() - is that needed?):

else {
    object originalProperty = sourceType.GetProperty(pi.Name).GetValue(this, null);
    object comparisonProperty = destinationType.GetProperty(pi.Name).GetValue(comparisonObject, null);

    if (originalProperty != comparisonProperty)
        return false;

The next suggestion would be to minimise the use of reflection as much as possible - it's really slow. I mean, really slow. If you are going to do this, I would suggest caching the property references. I'm not intimately familiar with the Reflection API, so if this is a bit off, just adjust to make it compile:

// elsewhere
Dictionary<object, Property[]> lookupDictionary = new Dictionary<object, Property[]>;

Property[] objectProperties = null;
if (lookupDictionary.ContainsKey(sourceType)) {
  objectProperties = lookupProperties[sourceType];
} else {
  // build array of Property references
  PropertyInfo[] sourcePropertyInfos = sourceType.GetProperties();
  Property[] sourceProperties = new Property[sourcePropertyInfos.length];
  for (int i=0; i < sourcePropertyInfos.length; i++) {
    sourceProperties[i] = sourceType.GetProperty(pi.Name);
  }
  // add to cache
  objectProperties = sourceProperties;
  lookupDictionary[object] = sourceProperties;
}

// loop through and compare against the instances

However, I have to say that I agree with the other posters. This smells lazy and inefficient. You should be implementing IComparable instead :-).

Elmer

I was just looking at IComparable but it seemed like it was for sorting and ordering.. is it really useful for comparing the equality of two objects? – Conveyance

Absolutely, because .Equals(object o) is defined as this.CompareTo(o) == 0. So, equals uses ComparesTo() to determine equality. This will be much more efficient (and standard practice) than using reflection. – Elmer

I may be mistaken assuming that Equals is implemented (or should be implemented) with reference to CompareTo(). You should consider overriding Equals as described here: #104658 – Elmer

Answer 11

here is revised one to treat null = null as equal

 private bool PublicInstancePropertiesEqual<T>(T self, T to, params string[] ignore) where T : class
        {
            if (self != null && to != null)
            {
                Type type = typeof(T);
                List<string> ignoreList = new List<string>(ignore);
                foreach (PropertyInfo pi in type.GetProperties(BindingFlags.Public | BindingFlags.Instance))
                {
                    if (!ignoreList.Contains(pi.Name))
                    {
                        object selfValue = type.GetProperty(pi.Name).GetValue(self, null);
                        object toValue = type.GetProperty(pi.Name).GetValue(to, null);
                        if (selfValue != null)
                        {
                            if (!selfValue.Equals(toValue))
                                return false;
                        }
                        else if (toValue != null)
                            return false;
                    }
                }
                return true;
            }
            return self == to;
        }

Bobbee

What if I had a deep object graph what's the best way to use above to return a list of old and new properties that were changed? – Dilley

Answer 12

I ended up doing this:

    public static string ToStringNullSafe(this object obj)
    {
        return obj != null ? obj.ToString() : String.Empty;
    }
    public static bool Compare<T>(T a, T b)
    {
        int count = a.GetType().GetProperties().Count();
        string aa, bb;
        for (int i = 0; i < count; i++)
        {
            aa = a.GetType().GetProperties()[i].GetValue(a, null).ToStringNullSafe();
            bb = b.GetType().GetProperties()[i].GetValue(b, null).ToStringNullSafe();
            if (aa != bb)
            {
                return false;
            }
        }
        return true;
    }

Usage:

    if (Compare<ObjectType>(a, b))

Update

If you want to ignore some properties by name:

    public static string ToStringNullSafe(this object obj)
    {
        return obj != null ? obj.ToString() : String.Empty;
    }
    public static bool Compare<T>(T a, T b, params string[] ignore)
    {
        int count = a.GetType().GetProperties().Count();
        string aa, bb;
        for (int i = 0; i < count; i++)
        {
            aa = a.GetType().GetProperties()[i].GetValue(a, null).ToStringNullSafe();
            bb = b.GetType().GetProperties()[i].GetValue(b, null).ToStringNullSafe();
            if (aa != bb && ignore.Where(x => x == a.GetType().GetProperties()[i].Name).Count() == 0)
            {
                return false;
            }
        }
        return true;
    }

Usage:

    if (MyFunction.Compare<ObjType>(a, b, "Id","AnotherProp"))

Excretion

Answer 13

You can optimize your code by calling GetProperties only once per type:

public static string ToStringNullSafe(this object obj)
{
    return obj != null ? obj.ToString() : String.Empty;
}
public static bool Compare<T>(T a, T b, params string[] ignore)
{
    var aProps = a.GetType().GetProperties();
    var bProps = b.GetType().GetProperties();
    int count = aProps.Count();
    string aa, bb;
    for (int i = 0; i < count; i++)
    {
        aa = aProps[i].GetValue(a, null).ToStringNullSafe();
        bb = bProps[i].GetValue(b, null).ToStringNullSafe();
        if (aa != bb && ignore.Where(x => x == aProps[i].Name).Count() == 0)
        {
            return false;
        }
    }
    return true;
}

Servo

Answer 14

For completeness I want to add reference to http://www.cyotek.com/blog/comparing-the-properties-of-two-objects-via-reflection It has more complete logic than most of others answers on this page.

However I prefer Compare-Net-Objects library https://github.com/GregFinzer/Compare-Net-Objects (referred by Liviu Trifoi's answer)
The library has NuGet package http://www.nuget.org/packages/CompareNETObjects and multiple options to configure.

Scriptorium

Answer 15

This works even if the objects are different. you could customize the methods in the utilities class maybe you want to compare private properties as well...

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

class ObjectA
{
    public string PropertyA { get; set; }
    public string PropertyB { get; set; }
    public string PropertyC { get; set; }
    public DateTime PropertyD { get; set; }

    public string FieldA;
    public DateTime FieldB;
}

class ObjectB
{
    public string PropertyA { get; set; }
    public string PropertyB { get; set; }
    public string PropertyC { get; set; }
    public DateTime PropertyD { get; set; }


    public string FieldA;
    public DateTime FieldB;


}

class Program
{
    static void Main(string[] args)
    {
        // create two objects with same properties
        ObjectA a = new ObjectA() { PropertyA = "test", PropertyB = "test2", PropertyC = "test3" };
        ObjectB b = new ObjectB() { PropertyA = "test", PropertyB = "test2", PropertyC = "test3" };

        // add fields to those objects
        a.FieldA = "hello";
        b.FieldA = "Something differnt";

        if (a.ComparePropertiesTo(b))
        {
            Console.WriteLine("objects have the same properties");
        }
        else
        {
            Console.WriteLine("objects have diferent properties!");
        }


        if (a.CompareFieldsTo(b))
        {
            Console.WriteLine("objects have the same Fields");
        }
        else
        {
            Console.WriteLine("objects have diferent Fields!");
        }

        Console.Read();
    }
}

public static class Utilities
{
    public static bool ComparePropertiesTo(this Object a, Object b)
    {
        System.Reflection.PropertyInfo[] properties = a.GetType().GetProperties(); // get all the properties of object a

        foreach (var property in properties)
        {
            var propertyName = property.Name;

            var aValue = a.GetType().GetProperty(propertyName).GetValue(a, null);
            object bValue;

            try // try to get the same property from object b. maybe that property does
                // not exist! 
            {
                bValue = b.GetType().GetProperty(propertyName).GetValue(b, null);
            }
            catch
            {
                return false;
            }

            if (aValue == null && bValue == null)
                continue;

            if (aValue == null && bValue != null)
                return false;

            if (aValue != null && bValue == null)
               return false;

            // if properties do not match return false
            if (aValue.GetHashCode() != bValue.GetHashCode())
            {
                return false;
            }
        }

        return true;
    }



    public static bool CompareFieldsTo(this Object a, Object b)
    {
        System.Reflection.FieldInfo[] fields = a.GetType().GetFields(); // get all the properties of object a

        foreach (var field in fields)
        {
            var fieldName = field.Name;

            var aValue = a.GetType().GetField(fieldName).GetValue(a);

            object bValue;

            try // try to get the same property from object b. maybe that property does
            // not exist! 
            {
                bValue = b.GetType().GetField(fieldName).GetValue(b);
            }
            catch
            {
                return false;
            }

            if (aValue == null && bValue == null)
               continue;

            if (aValue == null && bValue != null)
               return false;

            if (aValue != null && bValue == null)
               return false;


            // if properties do not match return false
            if (aValue.GetHashCode() != bValue.GetHashCode())
            {
                return false;
            }
        }

        return true;
    }


}

Topping

That code is not 100% efficient. it does not work in some situations for example if it contains a property of type object. – Topping

Answer 16

Update on Liviu's answer above - CompareObjects.DifferencesString has been deprecated.

This works well in a unit test:

CompareLogic compareLogic = new CompareLogic();
ComparisonResult result = compareLogic.Compare(object1, object2);
Assert.IsTrue(result.AreEqual);

Flagging

It's great that you fixed the depracation, but I think this answer should actually be a comment in the Liviu's answer. Specially because your sample code (compared to Liviu's) lacks the parameters of CompareLogic (which I'm sure are important), and also the assert message (which was the deprecated one). The assert can be fixed with: Assert.IsTrue(result.AreEqual, result.DifferencesString); – Imperishable

Answer 17

This method will get properties of the class and compare the values for each property. If any of the values are different, it will return false, else it will return true.

public static bool Compare<T>(T Object1, T object2)
{
    //Get the type of the object
    Type type = typeof(T);

    //return false if any of the object is false
    if (Object1 == null || object2 == null)
        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;
}

Usage:

bool isEqual = Compare<Employee>(Object1, Object2)

Bonniebonns

Answer 18

To expand on @nawfal:s answer, I use this to test objects of different types in my unit tests to compare equal property names. In my case database entity and DTO.

Used like this in my test;

Assert.IsTrue(resultDto.PublicInstancePropertiesEqual(expectedEntity));



public static bool PublicInstancePropertiesEqual<T, Z>(this T self, Z to, params string[] ignore) where T : class
{
    if (self != null && to != null)
    {
        var type = typeof(T);
        var type2 = typeof(Z);
        var ignoreList = new List<string>(ignore);
        var unequalProperties =
           from pi in type.GetProperties(BindingFlags.Public | BindingFlags.Instance)
           where !ignoreList.Contains(pi.Name)
           let selfValue = type.GetProperty(pi.Name).GetValue(self, null)
           let toValue = type2.GetProperty(pi.Name).GetValue(to, null)
           where selfValue != toValue && (selfValue == null || !selfValue.Equals(toValue))
           select selfValue;
           return !unequalProperties.Any();
    }
    return self == null && to == null;
}

Interurban

Answer 19

sometimes you don't want to compare all public properties and want to compare only the subset of them, so in this case you can just move logic to compare the desired list of properties to abstract class

public abstract class ValueObject<T> where T : ValueObject<T>
{
    protected abstract IEnumerable<object> GetAttributesToIncludeInEqualityCheck();

    public override bool Equals(object other)
    {
        return Equals(other as T);
    }

    public bool Equals(T other)
    {
        if (other == null)
        {
            return false;
        }

        return GetAttributesToIncludeInEqualityCheck()
            .SequenceEqual(other.GetAttributesToIncludeInEqualityCheck());
    }

    public static bool operator ==(ValueObject<T> left, ValueObject<T> right)
    {
        return Equals(left, right);
    }

    public static bool operator !=(ValueObject<T> left, ValueObject<T> right)
    {
        return !(left == right);
    }

    public override int GetHashCode()
    {
        int hash = 17;
        foreach (var obj in this.GetAttributesToIncludeInEqualityCheck())
            hash = hash * 31 + (obj == null ? 0 : obj.GetHashCode());

        return hash;
    }
}

and use this abstract class later to compare the objects

public class Meters : ValueObject<Meters>
{
    ...

    protected decimal DistanceInMeters { get; private set; }

    ...

    protected override IEnumerable<object> GetAttributesToIncludeInEqualityCheck()
    {
        return new List<Object> { DistanceInMeters };
    }
}

Missis

Answer 20

my solution inspired from Aras Alenin answer above where I added one level of object comparison and a custom object for comparison results. I am also interested to get property name with object name:

    public static IEnumerable<ObjectPropertyChanged> GetPublicSimplePropertiesChanged<T>(this T previous, T proposedChange,
     string[] namesOfPropertiesToBeIgnored) where T : class
    {
        return GetPublicGenericPropertiesChanged(previous, proposedChange, namesOfPropertiesToBeIgnored, true, null, null);
    }

    public static IReadOnlyList<ObjectPropertyChanged> GetPublicGenericPropertiesChanged<T>(this T previous, T proposedChange,
        string[] namesOfPropertiesToBeIgnored) where T : class
    {
        return GetPublicGenericPropertiesChanged(previous, proposedChange, namesOfPropertiesToBeIgnored, false, null, null);
    }

    /// <summary>
    /// Gets the names of the public properties which values differs between first and second objects.
    /// Considers 'simple' properties AND for complex properties without index, get the simple properties of the children objects.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="previous">The previous object.</param>
    /// <param name="proposedChange">The second object which should be the new one.</param>
    /// <param name="namesOfPropertiesToBeIgnored">The names of the properties to be ignored.</param>
    /// <param name="simpleTypeOnly">if set to <c>true</c> consider simple types only.</param>
    /// <param name="parentTypeString">The parent type string. Meant only for recursive call with simpleTypeOnly set to <c>true</c>.</param>
    /// <param name="secondType">when calling recursively, the current type of T must be clearly defined here, as T will be more generic (using base class).</param>
    /// <returns>
    /// the names of the properties
    /// </returns>
    private static IReadOnlyList<ObjectPropertyChanged> GetPublicGenericPropertiesChanged<T>(this T previous, T proposedChange,
        string[] namesOfPropertiesToBeIgnored, bool simpleTypeOnly, string parentTypeString, Type secondType) where T : class
    {
        List<ObjectPropertyChanged> propertiesChanged = new List<ObjectPropertyChanged>();

        if (previous != null && proposedChange != null)
        {
            var type = secondType == null ? typeof(T) : secondType;
            string typeStr = parentTypeString + type.Name + ".";
            var ignoreList = namesOfPropertiesToBeIgnored.CreateList();
            IEnumerable<IEnumerable<ObjectPropertyChanged>> genericPropertiesChanged =
                from pi in type.GetProperties(BindingFlags.Public | BindingFlags.Instance)
                where !ignoreList.Contains(pi.Name) && pi.GetIndexParameters().Length == 0 
                    && (!simpleTypeOnly || simpleTypeOnly && pi.PropertyType.IsSimpleType())
                let firstValue = type.GetProperty(pi.Name).GetValue(previous, null)
                let secondValue = type.GetProperty(pi.Name).GetValue(proposedChange, null)
                where firstValue != secondValue && (firstValue == null || !firstValue.Equals(secondValue))
                let subPropertiesChanged = simpleTypeOnly || pi.PropertyType.IsSimpleType()
                    ? null
                    : GetPublicGenericPropertiesChanged(firstValue, secondValue, namesOfPropertiesToBeIgnored, true, typeStr, pi.PropertyType)
                let objectPropertiesChanged = subPropertiesChanged != null && subPropertiesChanged.Count() > 0
                    ? subPropertiesChanged
                    : (new ObjectPropertyChanged(proposedChange.ToString(), typeStr + pi.Name, firstValue.ToStringOrNull(), secondValue.ToStringOrNull())).CreateList()
                select objectPropertiesChanged;

            if (genericPropertiesChanged != null)
            {   // get items from sub lists
                genericPropertiesChanged.ForEach(a => propertiesChanged.AddRange(a));
            }
        }
        return propertiesChanged;
    }

Using the following class to store comparison results

[System.Serializable]
public class ObjectPropertyChanged
{
    public ObjectPropertyChanged(string objectId, string propertyName, string previousValue, string changedValue)
    {
        ObjectId = objectId;
        PropertyName = propertyName;
        PreviousValue = previousValue;
        ProposedChangedValue = changedValue;
    }

    public string ObjectId { get; set; }

    public string PropertyName { get; set; }

    public string PreviousValue { get; set; }

    public string ProposedChangedValue { get; set; }
}

And a sample unit test:

    [TestMethod()]
    public void GetPublicGenericPropertiesChangedTest1()
    {
        // Define objects to test
        Function func1 = new Function { Id = 1, Description = "func1" };
        Function func2 = new Function { Id = 2, Description = "func2" };
        FunctionAssignment funcAss1 = new FunctionAssignment
        {
            Function = func1,
            Level = 1
        };
        FunctionAssignment funcAss2 = new FunctionAssignment
        {
            Function = func2,
            Level = 2
        };

        // Main test: read properties changed
        var propertiesChanged = Utils.GetPublicGenericPropertiesChanged(funcAss1, funcAss2, null);

        Assert.IsNotNull(propertiesChanged);
        Assert.IsTrue(propertiesChanged.Count == 3);
        Assert.IsTrue(propertiesChanged[0].PropertyName == "FunctionAssignment.Function.Description");
        Assert.IsTrue(propertiesChanged[1].PropertyName == "FunctionAssignment.Function.Id");
        Assert.IsTrue(propertiesChanged[2].PropertyName == "FunctionAssignment.Level");
    }

Janniejanos