==null e is null

using System;

namespace Nullable_2
{
  class Program
  {
    //differenze tra ==null e is null
    static void Main(string[] args)
    {
      var x = new MyClass();

      if (x == null) { Console.WriteLine("Test 1: x is null"); }

      if (x != null) { Console.WriteLine("Test 2: x is not null"); }

      if (x is null) { Console.WriteLine("Test 3: x is null"); }

      if (!(x is null)) { Console.WriteLine("Test 4: x is not null"); }

      if (x is object) { Console.WriteLine("Test 5: x is not null"); }

      if (!(x is object)) { Console.WriteLine("Test 6: x is null"); }

      if (x is { }) { Console.WriteLine("Test 7: x is not null"); }

      if (!(x is { })) {  Console.WriteLine("Test 8: x is null");}

      //c# 9
      //if (x is not null)
      //  {
      //  Console.WriteLine("Test 9: x is null");
      //}
    }

#nullable enable
    static void f(string? s) => Console.WriteLine(s!.Length);

  }

  public class MyClass
  {
    public static bool operator ==(MyClass left, MyClass right) { return true; }
    public static bool operator !=(MyClass left, MyClass right) { return true; }
  }
}