using System;

public class Program

{

    public static void Main()

    {

        var nilCheck = string.Equals("default", null, StringComparison.InvariantCultureIgnoreCase);

        var emptyCheck = string.Equals(null, null);

        var stringCheck = "default".Equals(null);

        Console.WriteLine(nilCheck);

        Console.WriteLine(emptyCheck);

        Console.WriteLine(stringCheck);

;   }

}