c# - How to raise custom event from a Static Class

Question

I have a static class that I would like to raise an event as part of a try catch block within a static method of that class.

For example in this method I would like to raise a custom event in the catch.

public static void saveMyMessage(String message)
{
    try
    {
        //Do Database stuff
    }
    catch (Exception e)
        {
              //Raise custom event here
        }
}

Thank you.

Answer 1

Important: be very careful about subscribing to a static event from instances. Static-to-static is fine, but a subscription from a static event to an instance handler is a great (read: very dangerous) way to keep that instance alive forever. GC will see the link, and will not collect the instance unless you unsubscribe (or use something like a WeakReference).

The pattern for creating static events is the same as instance events, just with static:

public static event EventHandler SomeEvent;

To make life easier (re null checking), a useful trick here is to add a trivial handler:

public static event EventHandler SomeEvent = delegate {};

Then you can simply invoke it without the null-check:

SomeEvent(null, EventArgs.Empty);

Note that because delegate instances are immutable, and de-referencing is thread-safe, there is never a race condition here, and no need to lock... who-ever is subscribed when we de-reference gets invoked.

(adjust for your own event-args etc). This trick applies equally to instance events.