using System;

using System.IO;

​

namespace supervillian

{

    public class Program

    {

        public static void Main(string[] args)

        {

            var superman = new Hero { Name = "Superman"};

            var batman = new Hero { Name = "Batman" };

​

            var heroes = new [] {

                superman,

                batman

            };

            /* Wrong Way To Null Check */

            Console.WriteLine("Evil At Work!");

            foreach(var hero in heroes) {

                var hereToSaveTheDay = hero == null

                    ? "Oh No!"

                    : "Yes!";

​

                Console.WriteLine(

                    $"Can {hero.Name} Save The Day? {hereToSaveTheDay}"

                );

            }

            Console.WriteLine();

​

            /* Right Way To Null Check */

            Console.WriteLine("But wait...");

            foreach(var hero in heroes) {

                var hereToSaveTheDay = hero is null

                    ? "Oh No!"

                    : "Yes!";

​

                Console.WriteLine(

                    $"Can {hero.Name} Save The Day? {hereToSaveTheDay}"

                );

            }

        }

    }

​

    public class Hero

    {

        public string Name { get; set; }

​

        public static bool operator ==(Hero first, Hero second) {

            if (first is null || second is null) {

                // lie

                return true;

            }

​

            return first.Name == second.Name;

        }

​

        public static bool operator !=(Hero first, Hero second) {

            if (first is null || second is null) {

                // lie

                return false;

            }

​

            return first.Name == second.Name;

        }

​

        public override int GetHashCode() {

            return (Name?.GetHashCode()).GetValueOrDefault();

        }

​

        public override bool Equals(object obj) {

            return (Name?.Equals(obj)).GetValueOrDefault();

        }

    }

}

​