using System;

using System.Collections.Concurrent;

using System.Collections.Generic;

using System.Linq;

using System.Threading.Tasks;

​

public class Sample

    {

​

        public string Firstname { get; }

        public string Lastname { get; }

​

        public Sample(string firstname, string lastname)

        {

            Firstname = firstname;

            Lastname = lastname;

        }

​

        public static bool operator ==(Sample obj1, Sample obj2) => false;

​

        public static bool operator !=(Sample obj1, Sample obj2) => true;

    }

​

class Program

{

  static async Task Main(string[] args)

  {

      Sample test = default;

      if (test is null) Console.WriteLine("YES it is NULL (test is null)");

      if (test == null) Console.WriteLine("YES it is NULL (test == null)");

  }

}