using System;

using System.Collections.Generic;

using System.Linq;

using System.ComponentModel.DataAnnotations;

using System.Reflection;

public class Program {

    public static void Main() {

        var p1 = new Person{

            Id = Guid.NewGuid(),

            FirstName = "John",

            LastName = "Smith",

            Age = 21,

            HairColor = "Brown"

        };

        var p2 = new Person{

            Id = Guid.NewGuid(),

            FirstName = "Jane",

            LastName = "Doe",

            Age = 23,

            HairColor = "Brown"

        };

        var variances = p1.Compare(p2);

        var props = variances.Aggregate(string.Empty, (a, next) => $"{ a }\r\n\t{ next.PropertyName }: { next.valA } | { next.valB }");

        Console.WriteLine($"There were { variances.Count } variances on these properties: { props }");

    }

}

​

public class Variance {

    public string PropertyName { get; set; }

    public object valA { get; set; }

    public object valB { get; set; }

}

​

public static class Comparision {

    public static List<Variance> Compare<T>(this T val1, T val2) {

        var variances = new List<Variance>();

        var properties = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance);

        foreach (var property in properties) {

            var name = property.GetCustomAttribute<DisplayAttribute>()?.Name;

            var v = new Variance {

                PropertyName = name ?? property.Name,

                valA = property.GetValue(val1),

                valB = property.GetValue(val2)

            };

            if (v.valA == null && v.valB == null) {

                continue;

            }

            if (

                (v.valA == null && v.valB != null)

                ||

                (v.valA != null && v.valB == null)

            ) {

                variances.Add(v);

                continue;

            }

            if (!v.valA.Equals(v.valB)) {

                variances.Add(v);

            }

        }

        return variances;

    }

}

​

public class Person {

    [Display(Name = "Person Id")]

    public Guid Id { get; set; }

    [Display(Name = "Person Firstname")]

    public string FirstName { get; set; }

    public string LastName { get; set; }

    public int Age { get; set; }

    public string HairColor { get; set; }

}