title: Prevent hiding of ModalPopupExtender when ok or cancel is clicked
body: <p>I am using an ASP.NET <code>ModalPopupExtender</code> on a page and would like to prevent the dialog from hiding when the user presses the ok button in certain conditions.  But I can't seem to find a way.</p>
  <p>What I am looking for is something like this</p>
  <pre><code>ajax:ModalPopupExtender
  ...
  OnOkScript=&quot;return confirm('You sure?')&quot;
  ...
  </code></pre>
  <p>if confirm is false, then the modal dialog doesn't disappear.</p>