Using Objects Comparer To Compare Complex Objects In C#

Introduction

It is quite a common situation when complex objects need to be compared. Sometimes, objects can contain nested elements, or some members should be excluded from the comparison (like auto-generated identifiers, create/update date, etc.), or some members can have custom comparison rules (same data in different formats, like phone numbers). This small framework was developed to solve such kinds of problems.

Briefly, Objects Comparer is an object-to-object comparer that allows us to compare objects recursively member by member and to define custom comparison rules for certain properties, fields, or types.

Objects Comparer can be considered as a ready-to-use framework or as a starting point for similar solutions.

Now, Objects Comparer supports enumerables (arrays, collections, lists), multidimensional arrays, enumerations, flags, and dynamic objects (ExpandoObject, DynamicObject, and compiler-generated dynamic objects).

Installation

Objects Comparer can be installed as a NuGet package.

Install-Package ObjectsComparer

Source code can be found on GitHub.

What's new in version 1.1

Dynamic objects support (ExpandoObject, DynamicObject, and compiler-generated dynamic objects)
Overriding comparison rule by member name
Overriding comparison rule by type and by name with filter
The DifferenceType property was added to the Difference class.

If you use version 1.0.x, you do not need to make any changes to start using version 1.1.

Basic Examples

To show how to use Objects Comparer, let's create 2 classes.

public class ClassA  
{  
    public string StringProperty { get; set; }  
  
    public int IntProperty { get; set; }  
  
    public SubClassA SubClass { get; set; }  
}  
  
public class SubClassA  
{  
    public bool BoolProperty { get; set; }  
}

There are some examples below how Objects Comparer can be used to compare instances of these classes.

//Initialize objects and comparer  
var a1 = new ClassA { StringProperty = "String", IntProperty = 1 };  
var a2 = new ClassA { StringProperty = "String", IntProperty = 1 };  
var comparer = new Comparer<ClassA>();  
  
//Compare objects  
IEnumerable<Difference> differences;  
var isEqual = comparer.Compare(a1, a2, out differences);  
  
//Print results  
Debug.WriteLine(isEqual ? "Objects are equal" : string.Join(Environment.NewLine, differences));

Objects are equal

In examples below, Compare objects and Print results blocks will be skipped for brevity except some cases.

var a1 = new ClassA { StringProperty = "String", IntProperty = 1 };  
var a2 = new ClassA { StringProperty = "String", IntProperty = 2 };  
var comparer = new Comparer<ClassA>();

Difference: DifferenceType=ValueMismatch, MemberPath='IntProperty', Value1='1', Value2='2'.

var a1 = new ClassA { SubClass = new SubClassA { BoolProperty = true } };  
var a2 = new ClassA { SubClass = new SubClassA { BoolProperty = false } };  
var comparer = new Comparer<ClassA>();

Difference: DifferenceType=ValueMismatch, MemberPath='SubClass.BoolProperty', Value1='True', Value2='False'.

Enumerables (arrays, collections, lists, etc.)

In this case, the enumerables can have different number of elements or some elements can have different values. Enumerables can be generic or non-generic. In case of non-generic enumerables, elements with the same index will be compared if types of these elements are equal, otherwise the difference with DifferenceType=TypeMismatch will be added to the list of differences.

var a1 = new[] { 1, 2, 3 };  
var a2 = new[] { 1, 2, 3 };  
var comparer = new Comparer<int[]>();

Objects are equal

var a1 = new[] { 1, 2 };  
var a2 = new[] { 1, 2, 3 };  
var comparer = new Comparer<int[]>();

Difference: DifferenceType=ValueMismatch, MemberPath='Length', Value1='2', Value2='3'.

var a1 = new[] { 1, 2, 3 };  
var a2 = new[] { 1, 4, 3 };  
var comparer = new Comparer<int[]>();

Difference: DifferenceType=ValueMismatch, MemberPath='[1]', Value1='2', Value2='4'.

var a1 = new ArrayList { "Str1", "Str2" };  
var a2 = new ArrayList { "Str1", 5 };  
var comparer = new Comparer<ArrayList>();

Difference: DifferenceType=TypeMismatch, MemberPath='[1]', Value1='Str2', Value2='5'.

Multidimensional arrays

var a1 = new[] { new[] { 1, 2 } };  
var a2 = new[] { new[] { 1, 3 } };  
var comparer = new Comparer<int[][]>();

Difference: DifferenceType=ValueMismatch, MemberPath='[0][1]', Value1='2', Value2='3'.

var a1 = new[] { new[] { 1, 2 } };  
var a2 = new[] { new[] { 2, 2 }, new[] { 3, 5 } };  
var comparer = new Comparer<int[][]>();

Difference: DifferenceType=ValueMismatch, MemberPath='Length', Value1='1', Value2='2'.

var a1 = new[] { new[] { 1, 2 }, new[] { 3, 5 } };  
var a2 = new[] { new[] { 1, 2 }, new[] { 3, 5, 6 } };  
var comparer = new Comparer<int[][]>();

Difference: DifferenceType=ValueMismatch, MemberPath='[1].Length', Value1='2', Value2='3'.

var a1 = new[,] { { 1, 2 }, { 1, 3 } };  
var a2 = new[,] { { 1, 3, 4 }, { 1, 3, 8 } };  
var comparer = new Comparer<int[,]>();

Difference: DifferenceType=ValueMismatch, MemberPath='Dimension1', Value1='2', Value2='3'.

var a1 = new[,] { { 1, 2 } };  
var a2 = new[,] { { 1, 3 } };  
var comparer = new Comparer<int[,]>();

Difference: DifferenceType=ValueMismatch, MemberPath='[0,1]', Value1='2', Value2='3'.

Dynamic objects

C# supports several types of objects, whose members can be dynamically added and removed at runtime.

ExpandoObject

If you are not familiar with how to use ExpandoObject, you can read this or search for another example.

dynamic a1 = new ExpandoObject();  
a1.Field1 = "A";  
a1.Field2 = 5;  
a1.Field4 = 4;  
dynamic a2 = new ExpandoObject();  
a2.Field1 = "B";  
a2.Field3 = false;  
a2.Field4 = "C";  
var comparer = new Comparer();

Difference: DifferenceType=ValueMismatch, MemberPath='Field1', Value1='A', Value2='B'.
Difference: DifferenceType=MissedMemberInSecondObject, MemberPath='Field2', Value1='5', Value2=''.
Difference: DifferenceType=TypeMismatch, MemberPath='Field4', Value1='4', Value2='C'.
Difference: DifferenceType=MissedMemberInFirstObject, MemberPath='Field3', Value1='', Value2='False'.

dynamic a1 = new ExpandoObject();  
a1.Field1 = "A";  
a1.Field2 = 5;  
dynamic a2 = new ExpandoObject();  
a2.Field1 = "B";  
a2.Field3 = false;  
var comparer = new Comparer();

Difference: DifferenceType=ValueMismatch, MemberPath='Field1', Value1='A', Value2='B'.
Difference: DifferenceType=MissedMemberInSecondObject, MemberPath='Field2', Value1='5', Value2=''.
Difference: DifferenceType=MissedMemberInFirstObject, MemberPath='Field3', Value1='', Value2='False'.

Behavior if member doesn't exist could be changed by providing custom ComparisonSettings (see Comparison Settings below).

dynamic a1 = new ExpandoObject();  
a1.Field1 = "A";  
a1.Field2 = 0;  
dynamic a2 = new ExpandoObject();  
a2.Field1 = "B";  
a2.Field3 = false;  
a2.Field4 = "S";  
var comparer = new Comparer(new ComparisonSettings { UseDefaultIfMemberNotExist = true });

Difference: DifferenceType=ValueMismatch, MemberPath='Field1', Value1='A', Value2='B'.
Difference: DifferenceType=ValueMismatch, MemberPath='Field4', Value1='', Value2='S'.

DynamicObject

DynamicObject is an abstract class and cannot be instantiated directly. Let’s assume that we have such an implementation of the DynamicObject class. It is necessary to have a correct implementation of the method GetDynamicMemberNames, otherwise, the Objects Comparer wouldn't work in the right way.

If you are not familiar with how to use DynamicObject, you can read this or search for another example.

private class DynamicDictionary : DynamicObject  
{  
    public int IntProperty { get; set; }  
  
    private readonly Dictionary<string, object> _dictionary = new Dictionary<string, object>();  
  
    public override bool TryGetMember(GetMemberBinder binder, out object result)  
    {  
        var name = binder.Name;  
  
        return _dictionary.TryGetValue(name, out result);  
    }  
  
    public override bool TrySetMember(SetMemberBinder binder, object value)  
    {  
        _dictionary[binder.Name] = value;  
  
        return true;  
    }  
  
    public override IEnumerable<string> GetDynamicMemberNames()  
    {  
        return _dictionary.Keys;  
    }  
}

dynamic a1 = new DynamicDictionary();  
a1.Field1 = "A";  
a1.Field3 = true;  
dynamic a2 = new DynamicDictionary();  
a2.Field1 = "B";  
a2.Field2 = 8;  
a2.Field3 = 1;  
var comparer = new Comparer();

Difference: DifferenceType=ValueMismatch, MemberPath='Field1', Value1='A', Value2='B'.
Difference: DifferenceType=TypeMismatch, MemberPath='Field3', Value1='True', Value2='1'.
Difference: DifferenceType=MissedMemberInFirstObject, MemberPath='Field2', Value1='', Value2='8'.

Compiler-generated objects

This type of dynamic object is the most popular and most easy to create.

dynamic a1 = new  
{  
    Field1 = "A",  
    Field2 = 5,  
    Field3 = true  
};  
dynamic a2 = new  
{  
    Field1 = "B",  
    Field2 = 8  
};  
var comparer = new Comparer();  
  
IEnumerable<Difference> differences;  
var isEqual = comparer.Compare((object)a1, (object)a2, out differences);

Difference: DifferenceType=ValueMismatch, MemberPath='Field1', Value1='A', Value2='B'.
Difference: DifferenceType=TypeMismatch, MemberPath='Field2', Value1='5', Value2='8'.
Difference: DifferenceType=MissedMemberInSecondObject, MemberPath='Field3', Value1='True', Value2=''.

This example requires some additional explanations. Types of the objects a1 and a2 were generated by the compiler and are considered as the same type if and only if objects a1 and a2 have the same set of members (same name and same type). If casting to (object) is skipped in case of a different set of members RuntimeBinderException will be thrown.

Overriding Comparison Rules

Sometimes some of the members require custom comparison logic. To override the comparison rule we need to create a custom value comparer or provide a function on how to compare objects and how to convert these objects to the string (optional) and filter function(optional). Value Comparer should be inherited from AbstractValueComparer or should implement IValueComparer.

public class MyValueComparer: AbstractValueComparer<string>  
{  
    public override bool Compare(string obj1, string obj2, ComparisonSettings settings)  
    {  
        return obj1 == obj2; //Implement comparison logic here  
    }  
}

Override the comparison rule for objects of a particular type.

//Use MyComparer to compare all members of type string   
comparer.AddComparerOverride<string>(new MyValueComparer());  
comparer.AddComparerOverride(typeof(string), new MyValueComparer());  
//Use MyComparer to compare all members of type string except members which name starts with "Xyz"  
comparer.AddComparerOverride(typeof(string), new MyValueComparer(), member => !member.Name.StartsWith("Xyz"));  
comparer.AddComparerOverride<string>(new MyValueComparer(), member => !member.Name.StartsWith("Xyz"));

Override the comparison rule for particular member (Field or Property). If toStringFunction parameter is not provided objects will be converted to string using ToString() method.

//Use MyValueComparer to compare StringProperty of ClassA  
comparer.AddComparerOverride(() => new ClassA().StringProperty, new MyValueComparer());  
comparer.AddComparerOverride(  
    typeof(ClassA).GetTypeInfo().GetMember("StringProperty").First(),  
    new MyValueComparer());  
//Compare StringProperty of ClassA by length. If length equal consider that values are equal  
comparer.AddComparerOverride(  
    () => new ClassA().StringProperty,  
    (s1, s2, parentSettings) => s1?.Length == s2?.Length,  
    s => s?.ToString());  
comparer.AddComparerOverride(  
    () => new ClassA().StringProperty,  
    (s1, s2, parentSettings) => s1?.Length == s2?.Length);

Override the comparison rule for particular member(s) (Field or Property) by name.

//Use MyValueComparer to compare all members with name equal to "StringProperty"  
comparer.AddComparerOverride("StringProperty", new MyValueComparer());

Overrides by type have the highest priority, then overrides by the member and overrides by member name have the lowest priority. If more than one of value comparers of the same type (by type/by name/by member name) could be applied to the same member, exception AmbiguousComparerOverrideResolutionException will be thrown during the comparison.

Example

var a1 = new ClassA();  
var a2 = new ClassA();  
comparer.AddComparerOverride<string>(valueComparer1, member => member.Name.StartsWith("String"));  
comparer.AddComparerOverride<string>(valueComparer2, member => member.Name.EndsWith("Property"));  
  
var result = comparer.Compare(a1, a2);//Exception here

Comparison Settings

Comparer constructor has an optional setting parameter to configure some aspects of comparison.

RecursiveComparison

True by default. If true, all members which are not primitive types, do not have custom comparison rules and do not implement ICompareble will be compared using the same rules as root objects.

EmptyAndNullEnumerablesEqual

False by default. If true, empty enumerable (arrays, collections, lists, etc.) and null values will be considered as equal values.

UseDefaultIfMemberNotExist

If true and the member does not exist, Objects Comparer will consider that this member is equal to the default value of the opposite member type. Applicable for dynamic types comparison only. False by default.

Comparison Settings class allows storing custom values that can be used in custom comparers.

SetCustomSetting<T>(T value, string key = null)  
GetCustomSetting<T>(string key = null)

Factory

Factory provides a way to encapsulate comparers' creation and configuration. Factory should implement IComparersFactory or should be inherited from ComparersFactory.

public class MyComparersFactory: ComparersFactory  
{  
    public override IComparer<T> GetObjectsComparer<T>(ComparisonSettings settings = null, IBaseComparer parentComparer = null)  
    {  
        if (typeof(T) == typeof(ClassA))  
        {  
            var comparer = new Comparer<ClassA>(settings, parentComparer, this);  
            comparer.AddComparerOverride<Guid>(new MyCustomGuidComparer());  
  
            return (IComparer<T>)comparer;  
        }  
  
        return base.GetObjectsComparer<T>(settings, parentComparer);  
    }  
}

Non-generic comparer

This comparer creates generic implementation of comparer for each comparison.

var comparer = new Comparer();  
var isEqual = comparer.Compare(a1, a2);

Useful Value Comparers

Framework contains several custom comparers that can be useful in many cases.

DoNotCompareValueComparer

Allows us to skip some fields/types. Has singleton implementation (DoNotCompareValueComparer.Instance).

DynamicValueComparer

Receives comparison rule as a function.

NulableStringsValueComparer

Null and empty strings are considered as equal values. Has singleton implementation (NulableStringsValueComparer.Instance).

DefaultValueValueComparer

Allows to consider the provided value and the default value of the specified type as equal values (see Example 3 below).

IgnoreCaseStringsValueComparer

Allows comparing string ignoring case. Has singleton implementation (IgnoreCaseStringsValueComparer.Instance).

Examples

There are some more complex examples of how Objects Comparer can be used.

Example 1 - Expected Message Challenge

Check if the received message equal to the expected message.

Problems

DateCreated, DateSent, and DateReceived properties need to be skipped
Auto-generated Id property need to be skipped
Message property of Error class need to be skipped

Solution

public class Error  
{  
    public int Id { get; set; }  
  
    public string Messgae { get; set; }  
}  
  
public class Message  
{  
    public string Id { get; set; }  
  
    public DateTime DateCreated { get; set; }  
  
    public DateTime DateSent { get; set; }  
  
    public DateTime DateReceived { get; set; }  
  
    public int MessageType { get; set; }  
  
    public int Status { get; set; }  
  
    public List<Error> Errors { get; set; }  
  
    public override string ToString()  
    {  
        return $"Id:{Id}, Type:{MessageType}, Status:{Status}";  
    }  
}

Configuring comparer

_comparer = new Comparer<Message>(  
    new ComparisonSettings  
    {  
        //Null and empty error lists are equal  
        EmptyAndNullEnumerablesEqual = true  
    });  
//Do not compare Dates   
_comparer.AddComparerOverride<DateTime>(DoNotCompareValueComparer.Instance);  
//Do not compare Id  
_comparer.AddComparerOverride(() => new Message().Id, DoNotCompareValueComparer.Instance);  
//Do not compare Message Text  
_comparer.AddComparerOverride(() => new Error().Messgae, DoNotCompareValueComparer.Instance);

var expectedMessage = new Message  
{  
    MessageType = 1,  
    Status = 0  
};  
  
var actualMessage = new Message  
{  
    Id = "M12345",  
    DateCreated = DateTime.Now,  
    DateSent = DateTime.Now,  
    DateReceived = DateTime.Now,  
    MessageType = 1,  
    Status = 0  
};  
  
IEnumerable<Difference> differences;  
var isEqual = _comparer.Compare(expectedMessage, actualMessage, out differences);

Objects are equal

var expectedMessage = new Message  
{  
    MessageType = 1,  
    Status = 1,  
    Errors = new List<Error>  
    {  
        new Error { Id = 2 },  
        new Error { Id = 7 }  
    }  
};  
  
var actualMessage = new Message  
{  
    Id = "M12345",  
    DateCreated = DateTime.Now,  
    DateSent = DateTime.Now,  
    DateReceived = DateTime.Now,  
    MessageType = 1,  
    Status = 1,  
    Errors = new List<Error>  
    {  
        new Error { Id = 2, Messgae = "Some error #2" },  
        new Error { Id = 7, Messgae = "Some error #7" },  
    }  
};  
  
IEnumerable<Difference> differences;  
var isEqual = _comparer.Compare(expectedMessage, actualMessage, out differences);

Objects are equal

var expectedMessage = new Message  
{  
    MessageType = 1,  
    Status = 1,  
    Errors = new List<Error>  
    {  
        new Error { Id = 2, Messgae = "Some error #2" },  
        new Error { Id = 8, Messgae = "Some error #8" }  
    }  
};  
  
var actualMessage = new Message  
{  
    Id = "M12345",  
    DateCreated = DateTime.Now,  
    DateSent = DateTime.Now,  
    DateReceived = DateTime.Now,  
    MessageType = 1,  
    Status = 2,  
    Errors = new List<Error>  
    {  
        new Error { Id = 2, Messgae = "Some error #2" },  
        new Error { Id = 7, Messgae = "Some error #7" }  
    }  
};  
  
IEnumerable<Difference> differences;  
var isEqual = _comparer.Compare(expectedMessage, actualMessage, out differences);

Difference: DifferenceType=ValueMismatch, MemberPath='Status', Value1='1', Value2='2'.
Difference: DifferenceType=ValueMismatch, MemberPath='Errors[1].Id', Value1='8', Value2='7'.

Example 2 Person comparison Challenge

Compare persons from different sources.

Problems

PhoneNumber format can be in different. Example: "111-555-8888" and "(111) 555 8888"
MiddleName can exist in one source but does not exist in another source. It makes sense to compare MiddleName only if it has value in both sources.
PersonId property need to be skipped

Solution

public class Person  
{  
    public Guid PersonId { get; set; }  
  
    public string FirstName { get; set; }  
  
    public string LastName { get; set; }  
  
    public string MiddleName { get; set; }  
  
    public string PhoneNumber { get; set; }  
  
    public override string ToString()  
    {  
        return $"{FirstName} {MiddleName} {LastName} ({PhoneNumber})";  
    }  
}

Phone number can have different formats. Let’s compare only digits.

public class PhoneNumberComparer: AbstractValueComparer<string>  
{  
    public override bool Compare(string obj1, string obj2, ComparisonSettings settings)  
    {  
        return ExtractDigits(obj1) == ExtractDigits(obj2);  
    }  
  
    private string ExtractDigits(string str)  
    {  
        return string.Join(  
            string.Empty,   
            (str ?? string.Empty)  
                .ToCharArray()  
                .Where(char.IsDigit));  
    }  
}

Factory allows not to configure comparer every time we need to create it.

public class MyComparersFactory: ComparersFactory  
{  
    public override IComparer<T> GetObjectsComparer<T>(ComparisonSettings settings = null, IBaseComparer parentComparer = null)  
    {  
        if (typeof(T) == typeof(Person))  
        {  
            var comparer = new Comparer<Person>(settings, parentComparer, this);  
            //Do not compare PersonId  
            comparer.AddComparerOverride<Guid>(DoNotCompareValueComparer.Instance);  
            //Sometimes MiddleName can be skipped. Compare only if property has value.  
            comparer.AddComparerOverride(  
                () => new Person().MiddleName,  
                (s1, s2, parentSettings) => string.IsNullOrWhiteSpace(s1) || string.IsNullOrWhiteSpace(s2) || s1 == s2);  
            comparer.AddComparerOverride(  
                () => new Person().PhoneNumber,  
                new PhoneNumberComparer());  
  
            return (IComparer<T>)comparer;  
        }  
  
        return base.GetObjectsComparer<T>(settings, parentComparer);  
    }  
}

Configuring comparer.

_factory = new MyComparersFactory();  
_comparer = _factory.GetObjectsComparer<Person>();

var person1 = new Person  
{  
    PersonId = Guid.NewGuid(),  
    FirstName = "John",  
    LastName = "Doe",  
    MiddleName = "F",  
    PhoneNumber = "111-555-8888"  
};  
var person2 = new Person  
{  
    PersonId = Guid.NewGuid(),  
    FirstName = "John",  
    LastName = "Doe",  
    PhoneNumber = "(111) 555 8888"  
};  
  
IEnumerable<Difference> differences;  
var isEqual = _comparer.Compare(person1, person2, out differences);

Objects are equal

var person1 = new Person  
{  
    PersonId = Guid.NewGuid(),  
    FirstName = "Jack",  
    LastName = "Doe",  
    MiddleName = "F",  
    PhoneNumber = "111-555-8888"  
};  
var person2 = new Person  
{  
    PersonId = Guid.NewGuid(),  
    FirstName = "John",  
    LastName = "Doe",  
    MiddleName = "L",  
    PhoneNumber = "222-555-9999"  
};  
  
IEnumerable<Difference> differences;  
var isEqual = _comparer.Compare(person1, person2, out differences);

Difference: DifferenceType=ValueMismatch, MemberPath='FirstName', Value1='Jack', Value2='John'.
Difference: DifferenceType=ValueMismatch, MemberPath='MiddleName', Value1='F', Value2='L'.
Difference: DifferenceType=ValueMismatch, MemberPath='PhoneNumber', Value1='111-555-8888', Value2='222-555-9999'.

Example 3 Comparing JSON configuration files Challenge

There are files with settings with some differences that need to be found. Json.NET is used to deserialize JSON data.

Problems

URLs can be with or without HTTP prefix.
DataCompression is Off by default
SmartMode1...3 disabled by default
ConnectionString, Email, and Notifications need to be skipped
If ProcessTaskTimeout or TotalProcessTimeout settings are skipped, the default values will be used. So, if in one file, a setting does not exist and in another file, this setting has a default value, it is actually the same.

Files Settings 0

{  
  "ConnectionString": "USER ID=superuser;PASSWORD=superpassword;DATA SOURCE=localhost:1111",  
  "Email": {  
    "Port": 25,  
    "Host": "MyHost.com",  
    "EmailAddress": "[email protected]"  
  },  
  "Settings": {  
    "DataCompression": "On",  
    "DataSourceType": "MultiDataSource",  
    "SomeUrl": "http://MyHost.com/VeryImportantData",  
    "SomeOtherUrl": "http://MyHost.com/NotSoImportantData/",  
    "CacheMode": "Memory",  
    "MaxCacheSize": "1GB",  
    "SuperModes": {  
      "SmartMode1": "Enabled",  
      "SmartMode2": "Disabled",  
      "SmartMode3": "Enabled"  
    }  
  },  
  "Timeouts": {  
    "TotalProcessTimeout": 500,  
    "ProcessTaskTimeout": 100  
  },  
  "BackupSettings": {  
    "BackupIntervalUnit": "Day",  
    "BackupInterval": 100  
  },  
  "Notifications": [  
    {  
      "Phone": "111-222-3333"  
    },  
    {  
      "Phone": "111-222-4444"  
    },  
    {  
      "EMail": "[email protected]"  
    }  
  ],  
  "Logging": {  
    "Enabled": true,  
    "Pattern": "Logs\\MyApplication.%data{yyyyMMdd}.log",  
    "MaximumFileSize": "20MB",  
    "Level": "ALL"  
  }  
}

Settings1

{  
  "ConnectionString": "USER ID=admin;PASSWORD=*****;DATA SOURCE=localhost:22222",  
  "Email": {  
    "Port": 25,  
    "Host": "MyHost.com",  
    "EmailAddress": "[email protected]"  
  },  
  "Settings": {  
    "DataCompression": "On",  
    "DataSourceType": "MultiDataSource",  
    "SomeUrl": "MyHost.com/VeryImportantData",  
    "SomeOtherUrl": "MyHost.com/NotSoImportantData/",  
    "CacheMode": "Memory",  
    "MaxCacheSize": "1GB",  
    "SuperModes": {  
      "SmartMode1": "enabled",  
      "SmartMode3": "enabled"  
    }  
  },  
  "BackupSettings": {  
    "BackupIntervalUnit": "Day",  
    "BackupInterval": 100  
  },  
  "Notifications": [  
    {  
      "Phone": "111-222-3333"  
    },  
    {  
      "EMail": "[email protected]"  
    }  
  ],  
  "Logging": {  
    "Enabled": true,  
    "Pattern": "Logs\\MyApplication.%data{yyyyMMdd}.log",  
    "MaximumFileSize": "20MB",  
    "Level": "ALL"  
  }  
}

Settings2

{  
  "ConnectionString": "USER ID=superuser;PASSWORD=superpassword;DATA SOURCE=localhost:1111",  
  "Email": {  
    "Port": 25,  
    "Host": "MyHost.com",  
    "EmailAddress": "[email protected]"  
  },  
  "Settings": {  
    "DataSourceType": "MultiDataSource",  
    "SomeUrl": "http://MyHost.com/VeryImportantData",  
    "SomeOtherUrl": "http://MyHost.com/NotSoImportantData/",  
    "CacheMode": "Memory",  
    "MaxCacheSize": "1GB",  
    "SuperModes": {  
      "SmartMode3": "Enabled"  
    }  
  },  
  "Timeouts": {  
    "TotalProcessTimeout": 500,  
    "ProcessTaskTimeout": 200  
  },  
  "BackupSettings": {  
    "BackupIntervalUnit": "Week",  
    "BackupInterval": 2  
  },  
  "Notifications": [  
    {  
      "EMail": "[email protected]"  
    }  
  ],  
  "Logging": {  
    "Enabled": false,  
    "Pattern": "Logs\\MyApplication.%data{yyyyMMdd}.log",  
    "MaximumFileSize": "40MB",  
    "Level": "ERROR"  
  }  
}

Configuring comparer.

_comparer = new Comparer(new ComparisonSettings { UseDefaultIfMemberNotExist = true });  
//Some fields should be ignored  
_comparer.AddComparerOverride("ConnectionString", DoNotCompareValueComparer.Instance);  
_comparer.AddComparerOverride("Email", DoNotCompareValueComparer.Instance);  
_comparer.AddComparerOverride("Notifications", DoNotCompareValueComparer.Instance);  
//Smart Modes are disabled by default. These fields are not case sensitive  
var disabledByDefaultComparer = new DefaultValueValueComparer<string>("Disabled", IgnoreCaseStringsValueComparer.Instance);  
_comparer.AddComparerOverride("SmartMode1", disabledByDefaultComparer);  
_comparer.AddComparerOverride("SmartMode2", disabledByDefaultComparer);  
_comparer.AddComparerOverride("SmartMode3", disabledByDefaultComparer);  
//http prefix in URLs should be ignored  
var urlComparer = new DynamicValueComparer<string>(  
    (url1, url2, settings) => url1.Trim('/').Replace(@"http://", string.Empty) == url2.Trim('/').Replace(@"http://", string.Empty));  
_comparer.AddComparerOverride("SomeUrl", urlComparer);  
_comparer.AddComparerOverride("SomeOtherUrl", urlComparer);  
//DataCompression is Off by default.  
_comparer.AddComparerOverride("DataCompression", new DefaultValueValueComparer<string>("Off", NulableStringsValueComparer.Instance));  
//ProcessTaskTimeout and TotalProcessTimeout fields have default values.  
_comparer.AddComparerOverride("ProcessTaskTimeout", new DefaultValueValueComparer<long>(100, DefaultValueComparer.Instance));  
_comparer.AddComparerOverride("TotalProcessTimeout", new DefaultValueValueComparer<long>(500, DefaultValueComparer.Instance));

var settings0Json = LoadJson("Settings0.json");  
var settings0 = JsonConvert.DeserializeObject<ExpandoObject>(settings0Json);  
var settings1Json = LoadJson("Settings1.json");  
var settings1 = JsonConvert.DeserializeObject<ExpandoObject>(settings1Json);  
  
IEnumerable<Difference> differences;  
var isEqual = _comparer.Compare(settings0, settings1, out differences);

Objects are equal

var settings0Json = LoadJson("Settings0.json");  
var settings0 = JsonConvert.DeserializeObject<ExpandoObject>(settings0Json);  
var settings2Json = LoadJson("Settings2.json");  
var settings2 = JsonConvert.DeserializeObject<ExpandoObject>(settings2Json);  
  
IEnumerable<Difference> differences;  
var isEqual = _comparer.Compare(settings0, settings2, out differences);

Difference: DifferenceType=ValueMismatch, MemberPath='Settings.DataCompression', Value1='On', Value2='Off'.
Difference: DifferenceType=ValueMismatch, MemberPath='Settings.SuperModes.SmartMode1', Value1='Enabled', Value2='Disabled'.
Difference: DifferenceType=ValueMismatch, MemberPath='Timeouts.ProcessTaskTimeout', Value1='100', Value2='200'.
Difference: DifferenceType=ValueMismatch, MemberPath='BackupSettings.BackupIntervalUnit', Value1='Day', Value2='Week'.
Difference: DifferenceType=ValueMismatch, MemberPath='BackupSettings.BackupInterval', Value1='100', Value2='2'.
Difference: DifferenceType=ValueMismatch, MemberPath='Logging.Enabled', Value1='True', Value2='False'.
Difference: DifferenceType=ValueMismatch, MemberPath='Logging.MaximumFileSize', Value1='20MB', Value2='40MB'.
Difference: DifferenceType=ValueMismatch, MemberPath='Logging.Level', Value1='ALL', Value2='ERROR'.

That's it. Enjoy.

13 Comments

Join the conversation! Your thoughts help the community grow.

ajith sj7y ago
DifferenceType=ValueMismatch, FiledName='FirstName', Expected='Jack', Actual='John'.
ajith sj7y ago
Is it possible to customize the message
- Valerii Tereshchenko7y ago
  What kind of customization?
Valerii Tereshchenko8y ago
Important Notice!!!If you have any issues with ObjectsComparer or ideas how it could be improved please create issue on GitHub. Reasons why: There are almost the same articles on Codeproject, DZone and Medium. That folks don't see your comments and you don't see theirs' comments. It would be much better to have all discussions in one place. GitHub provides much more functionality to work with issues.
Daniel8y ago
Hi Valerii, I've hit a problem with the ObjectComparer where I have a property on the class to be compared which is a Type (e.g. public Type _foo { get; set; }) and the Compare method is throwing this error: Exception has been thrown by the target of an invocation; Method may only be called on a Type for which Type.IsGenericParameter is true. -- the reason this is being thrown from what I can see is because Type is obviously not a generic type itself, and it looks like the Comparer is trying to use reflection and GetDeclaringMethod to build all of the properties - I want to ignore the field entirely, but the exception is thrown too early. Is there any way you could conditionally ignore non-generic types so this exception isn't thrown?
- Daniel8y ago
  Hi Valerii, It's great that this is going to be fixed in the next version, do you have any kind of timescales as to when it may be released? I have already tried adding the override but unfortunately the issue occurs when the comparer tries to activate the object and read all of the properties which seems to happen before the properties are then ignored (makes sense that you can't ignore a property until you've instantiated it!) Cheers Dan.
- Daniel8y ago
  Hi Valerii, I have just added your line of code and it now seems to be working, I don't know why my attempt didn't work the first time! Thanks so much. I look forward to the next version, keep up the great work!
- Valerii Tereshchenko8y ago
  Hi Daniel. You can skip comparing your property by overriding comparer: comparer.AddComparerOverride<Type>(DoNotCompareValueComparer.Instance);
Dan Ager8y ago
Just to say that this package is awesome and handles my dynamic and non dynamic objects perfectly with value and property comparisons and a great intuitive difference output. 880 downloads on Nuget when I started using this and I'd previously tried using CompareNetObjects which has nearly a million downloads and this is so much easier and better to use, not to mention the CompareNetObjects package couldn't handle dynamics in the way I needed it to!
- Valerii Tereshchenko8y ago
  Thanks a lot! I tried to make something simple and easy to use in majority of the cases.