private static void Main(string[] args)
{
IObservable observable = new Observable();
observable.AddObserver(new Observer("Something happend"));
var observer = new Observer("Wow!!!");
observable.AddObserver(observer);
observable.NotifyAllObservers();
observable.AddObserver(new Observer("Great"));
observable.NotifyAllObservers();
observable.RemoveObserver(observer);
observable.NotifyAllObservers();
Console.WriteLine("press <enter> to exit");
Console.ReadLine();
}