How to ensure an event is only subscribed to once

c# events event-handling subscription
Glen T picture Glen T · Dec 15, 2008 · Viewed 27.3k times · Source

I would like to ensure that I only subscribe once in a particular class for an event on an instance.

For example I would like to be able to do the following:

if (*not already subscribed*)
{
    member.Event += new MemeberClass.Delegate(handler);
}

How would I go about implementing such a guard?

Answer

alf picture alf · Aug 15, 2011

I'm adding this in all the duplicate questions, just for the record. This pattern worked for me:

myClass.MyEvent -= MyHandler;
myClass.MyEvent += MyHandler;

Note that doing this every time you register your handler will ensure that your handler is registered only once.

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