using System;

public class Program

{

    public static void Main()

    {

        var bob = new Bob();

        Bob bob2 = null;

​

        bob.OnNullExtension();

        bob2.OnNullExtension();

    }

}

​

public class Bob

{

    public int Id { get; set; } 

}

​

public static class BobExtensions

{

    public static void OnNullExtension(this Bob self)

    {

        if (self == null)

        {

            Console.WriteLine("Safe exit!");

            return;

        }

​

        Console.WriteLine("I'm not null!");

    }

}