asp.net checkbox modalpopupextender checkbox doesn't check or uncheck

There is an apparent bug in asp.net that when you have a checkbox inside a panel that is acting as a modal popup with the modalpopupextender, that when you try to check or uncheck it, it doesn't work!

I found the following thread, and it seems that quite a few people have had this very same problem.

From reading many posts, it seems that this happens if you do not set the TargetControlID property of the extender correctly.

However, this becomes an issue if you have multiple links, all that show the same extender. To get round this, you can simply create a fake button:



And then in your modal extender, set TargetControlID="btnFakeButton". With your links / buttons to active this, simply in the code behind for the event for each link / button, do mdlExample.Show() to display the modal.