using System;

​

public static class CarExtensions

{

    public static void Beep(this Program.Car car)

    {

        // Note: car.make instead of car?.make

        Console.WriteLine("Car with make: " + car.make + " beeps. Beep! Beep!");

    }

}

​

public class Program

{

    public class Car

    {

        public int make { get; set; }

​

        public Car(int make)

        {

            this.make = make;

        }

    }

​

    public static void Main()

    {

        Car car = new Car(1999);

        Car carNull = null;

        // Here we are going to try out our horn. Beep beep.

        car.Beep();

        carNull?.Beep();

        // The second car is null, so only 1 beep.

        // But we did not get a null reference exception. Meaning that car.make is sufficient, we dont need car?.make 

    }

}