I have a base page in which i have a listbox. The base page is also having a modal popup extender. When the modal popup extender appears over listbox, the listbox appears through modal poup. That is, only for listbox, the popup extender becomes transparent.
What shud I do for this?
My understanding is that, since listboxes/dropdowns are windows controls, they will always appear over the modal popup.
I haven't tested this, but your best bet may be to write some code in the button click handler that launches the popup and either diable or hide the offending control.