using System;

using System.Linq;

using System.Reflection;

using static System.Console;

public class Program

{

    public static void Main()

    {

        Klass m1 = new()

        {

            FieldA = "A",

            FieldB = "Different",

            FieldC = "C",

            FieldD = 100,

            FieldE = "E",

        };

​

        Klass m2 = new()

        {

            FieldB = "B",

            FieldC = "C",

            FieldD = 5,

            FieldE = "E"

        };

​

        var result = m1.Difference(m2);

        WriteLine(result);

    }

}

​

public static class ReflectionExtensions

{

    public static TModel Difference<TModel>(this TModel model1, TModel model2) where TModel : new()

    {

        static bool AreEqual(object obj1, object obj2) =>

            (obj1 is null && obj2 is null) ||

            obj1.Equals(obj2);

​

        Type type = typeof(TModel);

        PropertyInfo[] properties = type.GetProperties(BindingFlags.Public | BindingFlags.Instance);

​

        TModel result = properties.Aggregate(new TModel(), (seed, property) =>

        {

            var value1 = property.GetValue(model1);

            var value2 = property.GetValue(model2);

​

            if (!AreEqual(value1, value2))

            {

                property.SetValue(seed, value1);

            }

​

            return seed;

        });

​

        return result;

    }

}

​

public class Klass

{

    public string FieldA { get; set; }

    public string FieldB { get; set; }

    public string FieldC { get; set; }

    public int FieldD { get; set; }

    public string FieldE { get; set; }

    public override string ToString()

    {

        return $"{{ A = {FieldA}, B = {FieldB}, C = {FieldC}, D = {FieldD}, E = {FieldE} }}";

    }

}