接线和无线接线

Question

In some cases I have found, developers unwire event then wire it again like this:

control.Click -= new eventHandler(eventHandler)
control.Click += new eventHandler(eventHandler)

why do they do that?

Answer 1

Possibly because there is other code in between that will trigger the event, and they don't want eventHandler to act on it. IMHO this isn't the best way to do things, but it's easy and it works.

If there is no other code in between there cannot possibly be a reason to remove and add the same event handler again.

Answer 2

I can explain this in a simple screnerio.

Imagine you have a "button1" And you added the event on the run-time.

But once this button is clicked. The process behind it take let say "3Mins" to complete. And you don't want the user to click this button again.

So you can do by Unwiring it in the first time. So that the person don't click the button again and again. And adding the instruction in the queue.

Answer 3

If you call code that wires an event, and you don't wont to accidentally wire it up again if it was already wired, you can unwire, and then rewire it. This is the code sample above.

If it wasn't already wired in the first place, no error is thrown. But if the code had already been run first, you don't wont the event to run twice. Thus, unwire and then rewire.