Determine if an event has been attached to yet

Question

I have two objects - one that contains some code with will fire an event, and one that contains the handler for that event. I can't "AddHandler" in the Load of the first object, because an instance of the second object doesn't exist yet. When I raise my event, I want to check to see if a copy of object2 has been instantiated (easy to do), and if a handler has been attached to the event yet (not sure how to do this).

I'm also open to another recommendation about how to do this instead. If I do my AddHandler in Object1.Load, and Object2 doesn't exist yet, then it will never handle my event, even if I create it later. Right now, in the code that fires the event, I've just resorted to doing a RemoveHandler and then an AddHandler every single time the event is raised, and then I know I'll attach when the object finally exists, but I know this is a crappy method.

I saw an article about something similar (http://stackoverflow.com/questions/660480/determine-list-of-event-handlers-bound-to-event), and maybe I'm missing something in the translation, but I can't get the code to work on my custom event in VB.NET.

Answer 1

If you just want to know whether any handler has been attached, you should be able to check whether the event is null.

if (MyButton.Click == null)
{
    MyButton.Click += myEventHandler;
}

(I'll let you translate that into VB)

Answer 2

You could also just have a bool field that you check before hooking the event.

if not eventHooked then
 addhandler
 eventHooked = true
end if

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