The observer pattern is usually implemented with events. Here’s an example: using System; class Observable { public event EventHandler SomethingHappened; public void DoSomething() => SomethingHappened?.Invoke(this, EventArgs.Empty); } class Observer { public void HandleEvent(object sender, EventArgs args) { Console.WriteLine(“Something happened to ” + sender); } } class Test { static void Main() { Observable observable = … Read more
You need to use the Observer Pattern. In the following code, a person subscribes to receive updates from the global wealth entity. When there is a change to global wealth, this entity then alerts all its subscribers (observers) that a change happened. Person then updates itself. I make use of properties in this example, but … Read more
You have a concrete example of a Student and a MessageBoard. The Student registers by adding itself to the list of Observers that want to be notified when a new Message is posted to the MessageBoard. When a Message is added to the MessageBoard, it iterates over its list of Observers and notifies them that … Read more
Update 2016-06-27: instead of using Observables, use either a BehaviorSubject, as recommended by @Abdulrahman in a comment, or a ReplaySubject, as recommended by @Jason Goemaat in a comment A Subject is both an Observable (so we can subscribe() to it) and an Observer (so we can call next() on it to emit a new value). … Read more