protected override void RealTestOutPut() { var tracker = new DataTracker(); var tracker1 = new DataObserver("tracker1"); var tracker2 = new DataObserver("tracker2"); tracker1.Subscribe(tracker); tracker2.Subscribe(tracker); tracker.Track(new DataSource() { a = 888 }); tracker1.UnSubscribe(); tracker.Track(new DataSource() { a = 233 }); tracker.Track(null); }