The eventing mechanism built into the .NET runtime makes it a piece of cake to implement a simple publisher - subscriber pattern (C# code follows).   public class EmployerPublisher { public event PayrollArrivedHandler PayrollArrived; public void FireEvent(DateTime today) { if(PayrollArrived != null) PayrollArrived(today); } } // Subscriber class - Employee public class Employee { public void OnPayrollArrival(DateTime day) ... [More]