using System;

using System.Collections.Generic;

using System.Linq;

​

namespace ConsoleApp

{

    public class Person

    {

        public int Age { get; set; }

        public string FirstName { get; set; }

        public string LastName { get; set; }

​

        public Person(int age, string firstName, string lastName)

        {

            Age = age;

            FirstName = firstName;

            LastName = lastName;

        }

​

        public override string ToString()

        {

            return $"Age = {Age}, FirstName = {FirstName}, LastName = {LastName}";

        }

    }

​

    public class PersonEqualityComparer : IEqualityComparer<Person>

    {

        public bool Equals(Person x, Person y)

        {

            if (ReferenceEquals(x, y))

            {

                return true;

            }

​

            if (x is null || y is null)

            {

                return false;

            }

​

            return x.Age == y.Age && 

                   x.FirstName == y.FirstName && 

                   x.LastName == y.LastName;

        }

​

        public int GetHashCode(Person obj)

        {

            if (obj == null)

            {

                return 0;

            }

​

            return HashCode.Combine(obj.Age, obj.FirstName, obj.LastName);

        }

    }

​

    public class Program

    {

        public static void Main()

        {

            var list1 = new List<Person>

            {

                new Person(20, "first1", "last1"),

                new Person(30, "first2", "last2"),

                new Person(40, "first3", "last3"),

                new Person(50, "first4", "last4")

            };

​

            var list2 = new List<Person>

            {

                new Person(30, "first2", "last2"),

                new Person(50, "first4", "last4")

            };

​

            var list3 = list1.Except(list2, new PersonEqualityComparer());

​

            foreach (var person in list3)

            {

                Console.WriteLine(person);

            }

        }

    }

}