public static void Start() { LinkedIn observable = new LinkedIn(); UnemployedEngineer jack = new UnemployedEngineer(observable, "jack"); UnemployedHr emily = new UnemployedHr(observable, "emily"); UnemployedEngineer angely = new UnemployedEngineer(observable, "angely"); UnemployedHr john = new UnemployedHr(observable, "john"); observable.NewJobsAvailabel(); observable.UnRegisterObserver(jack); observable.UnRegisterObserver(angely); observable.NewJobsAvailabel(); observable.RegisterObserver(jack); observable.RegisterObserver(angely); observable.NewJobsAvailabelPullMode(); }