We all know the pattern to declare an event in C#, fairly easy, here is a remainder:

   1: public class EventTest

   2:         {

   3:             public event EventHandler MyEvent;

   4: 

   5:             public void RaiseEvent()

   6:             {

   7:                 if(MyEvent != null)

   8:                 {

   9:                     MyEvent(this, EventArgs.Empty);

  10:                 }

  11:             }

  12:         }

I know that many people forget to check that the event in not Null (meaning that someone has registered) before raising it and later on receive a well deserved exception :), and I know that many of you (including me) hate this pattern. Well, I am here to present you with a much more slick and usable pattern to declare events. In order to avoid that annoying Null check and make your code nicer, declare the event in the following way:

   1: public event EventHandler MyEvent = delegate {};

If you do it this way, you already have a delegate (an anonymous one) registered to the event and now, the event will never be null, so you can safely raise it without checking. Some would say that you are wasting resources but i think the Null check or an empty delegate are no big difference. The outcome is this much nicer class:

   1: public class EventTest

   2:         {

   3:             public event EventHandler MyEvent = delegate {};

   4: 

   5:             public void RaiseEvent()

   6:             {

   7:                 MyEvent(this, EventArgs.Empty);

   8:             }

   9:         }

About a week ago I wrote a post about why registering to events might cause your object not to get disposed. In this case the delegate belongs to the object being disposed , so both the object and his delegate loose the outside reference, hence, they will be disposed eventually.

Hope you like this idea as much as i did.

Amit

Tags: .Net, C#, Class, Event, Event Declaration, EventHandler, Pattern