using System;

using System.Linq.Expressions;

using System.Reflection;

public class Program

{

    public static void Main()       

    {

        var original = new TestEntity();

        original.Name = "test";

        var dto = new TestDTO();

        dto.FirstName = "New Value";

        UpdateIfDifferent(original, o => o.Name, dto, d => d.FirstName);

        Console.WriteLine(original.Name);

    }

    private static void UpdateIfDifferent<TOriginal, TOriginalProperty, TUpdated, TUpdatedProperty>

        (TOriginal original, Expression<Func<TOriginal, TOriginalProperty>> originalProperty, 

            TUpdated updated, Expression<Func<TUpdated, TUpdatedProperty>> updatedProperty)

    {

      if (!originalProperty.Compile()(original).Equals(updatedProperty.Compile()(updated)))  

      {

​

            var updatedMember = (updatedProperty.Body as MemberExpression).Member as PropertyInfo;

            var updatedValue = updatedMember.GetValue(updated);

​

            var member = (originalProperty.Body as MemberExpression).Member as PropertyInfo;

            member.SetValue(original, updatedValue);

        }

    }

    public class TestEntity

    {

        public string Name {get;set;}

    }

    public class TestDTO

    {

        public string FirstName {get;set;}

    }

}