Clearing/Discovering Control Events - ng.asp-net-forum.windows-hosting_open_forum

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7 Items, 1 Pages 1 |< << Go >> >|

	dasein_fiasco
	Asp.Net User

Clearing/Discovering Control Events

10/21/2005 4:53:23 PM

0/0

I have a pretty simple question here but for the life of me I can't find any answers elsewhere.

Given a control, I need to unwire all events registered for that control. For example, say I have a datagrid with ItemCommand, SortCommand, PageIndexChanged, and ItemDataBound events. I need a way to clear all those events from the control. Alternatively, I need a way to inspect the control to see if those events are already registered.

My problem is that the control is in danger of having the events registered multiple times, so I need a way to either clear out all previously registered events, or else I need to know whether or not the events have been registered.

Thanks in advance for any suggestions.

	master4eva
	Asp.Net User

Re: Clearing/Discovering Control Events

10/21/2005 7:52:34 PM

0/0

I smell a fish here in the design of your code. Isn't there any other way that you could implement your code without relying on removing function pointers?

-- Justin Lovell

	dasein_fiasco
	Asp.Net User

Re: Clearing/Discovering Control Events

10/21/2005 8:24:53 PM

0/0

Yes, definitely. But the situation arose out of an attempt to implement an optimization trick, and I'm keen to see if it can be pulled off.

The system is architectured to use dynamic composite controls, and profiling revealed the LoadControl() function to be one of the largest bottlenecks in the code. The solution was to load the controls less often, by storing the controls in the Session and pointing to them as needed. The problem is that the events will wire up to those stored controls each time that they load, and if the control has been loaded before, the events will simply stack up on it.

There are other ways to ensure that the events wire up once and only once, but nothing that's really as simple as simply clearing the events and rewiring on each load, or inspecting the events on the control to see if they need to be wired or not.

It's fishy insofar that it's kind of a quirky design, but it does result in substantial performance improvement, which is why it's being pursued.

	master4eva
	Asp.Net User

Re: Clearing/Discovering Control Events

10/21/2005 8:45:59 PM

0/0

In that case, why not do something like:

private void WireEvents(SomeControl c) {
   if (this.Page.Session["ControlLoaded"] == null) {
      // attach events over here.
      this.Page.Session["ControlLoaded"] = new object();
   }
}

// ...

SomeControl c = ...;

this.WireEvents(c);

And yes, I do understand the reasoning for this fishy solution Smile [:)]

-- Justin Lovell

	dasein_fiasco
	Asp.Net User

Re: Clearing/Discovering Control Events

10/21/2005 9:48:59 PM

0/0

What you just described was another option ? tracking whether or not the events had been wired. Alternatively, I was considering looping through the this.Events collection of the control, and removing each handler that way.

I suppose my question was more academic than it was essential ? is there an existing way to discover if a control has events, or to clear all such events, or else do I have to write a code snippet to handle this myself?

In any case, thanks for the responses. Even a simple "no" is reassuring in that I'll feel confident that I can cease pouring over msdn and google results for an answer.

	master4eva
	Asp.Net User

Re: Clearing/Discovering Control Events

10/22/2005 7:28:05 AM

0/0

I won't say that I know of definite answer as if you could remove specific handlers from events. There is no full solution as I know of one. You could discover which delegates are in the event list via something like this:

Delegate[] methodsToExecuteOnClick = this.button.Click.GetInvocationList();

However, that will give you pointers to the method information (ie: the method name to execute from which class). I did not suggest the above as the above operation is expensive and you were after performance Wink [;)]

.

That is the discovery method that I know of. However, I don't think you could remove it at all because I have the following scholar reasoning: adding delegates to an event should not allow another part of the application to remove it from the event. It is impractical as you may want the same delegate to be published twice (remember that list that you can only find which delegates have been added; not which object instance each one lives under).

-- Justin Lovell

	dasein_fiasco
	Asp.Net User

Re: Clearing/Discovering Control Events

10/22/2005 1:28:16 PM

0/0

I think I solved the problem in the following manner. In the Page_Load of my controls, I invoke the following code prior to wiring/rewiring events: this.Events.Dispose(). On first glance it seems to work beautifully.

7 Items, 1 Pages 1 |< << Go >> >|

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