static void Main(string[] args) { Console.WriteLine("Hello World!"); var subject = new Subject(); var greenObserver = new Observer(ConsoleColor.Green); var redObserver = new Observer(ConsoleColor.Red); var yellowObserver = new Observer(ConsoleColor.Yellow); subject.QuantityUpdated += greenObserver.OnUpdateQuantity; subject.QuantityUpdated += redObserver.OnUpdateQuantity; subject.QuantityUpdated += yellowObserver.OnUpdateQuantity; subject.AddToQuantity(12); subject.AddToQuantity(5); Console.WriteLine("Enter a key to quit."); Console.Read(); }