using Observer.Observers; namespace Observer { internal class Program { static void Main(string[] args) { var subject = new Subject(); var observerA = new ConcreteObserverA(); subject.Attach(observerA); var observerB = new ConcreteObserverB(); subject.Attach(observerB); subject.SomeBusinessLogic(); subject.SomeBusinessLogic(); subject.Detach(observerB); subject.SomeBusinessLogic(); } } }