public static void Main() { Group provider = new Group(); Subscriber observer1 = new Subscriber("User: Jovan Vulin"); Subscriber observer2 = new Subscriber("User: John Doe"); provider.handlePost(100, "Welcome users!", true); observer1.Subscribe(provider); observer2.Subscribe(provider); provider.handlePost(101, "C# patterns", true); //Invalid post, shouldn't be displayed provider.handlePost(100, "Welcome users!", true); provider.handlePost(100, "Test users!", true); provider.handlePost(100); provider.handlePost(102, "Observer pattern", true); Console.ReadLine(); }