static void Main(string[] args)
{
ConcreteSubject subject = new ConcreteSubject();
Observer observer1 = new ConcreteObserver();
Observer observer2 = new ConcreteObserver();
Observer observer3 = new ConcreteObserver();
Observer observer4 = new ConcreteObserver();
subject.Attach(observer1);
subject.Attach(observer2);
subject.Attach(observer3);
subject.Attach(observer4);
subject.Invoke();
Console.ReadKey();
}