static void Main(string[] args) { ChatRoom chatRoom = new ChatRoom(); User user1 = new User("user1"); User user2 = new User("user2"); User user3 = new User("user3"); chatRoom.Register(user1); chatRoom.Register(user2); chatRoom.Register(user3); chatRoom.Send("hello", user1, user2); user1.Send(user2, "hello 2"); Console.WriteLine(" "); chatRoom.SendAll("hello all"); }