How can I know if a .net event is already handled?

Question

I've written some code to handle an event as follows:

AddHandler myObject.myEvent, AddressOf myFunction

It seemed that everything was working at first, but when I ran the debugger, I discovered that oftentimes, myFunction would run several times each time myObject.myEvent fired. I figured out that I had allowed the code to add the event handler to run more than once, resulting in this behavior.

Is there a way I can do something like this?

If myObject.myEvent is not handled Then
  AddHandler myObject.myEvent, AddressOf myFunction
End If

Answer 1

Remove the handler and then add it. This way it will never be duplicated. Beware of the null reference error if your object does not exist. I got caught on that too and may happen when you are removing the handler outside the sub where the handler is created.

if not myObject is nothing then RemoveHandler myObject.myEvent, AddressOf myFunction
if not myObject is nothing then AddHandler myObject.myEvent, AddressOf myFunction