PopupControl is an ASP.NET AJAX extender that can be attached to any control in order to open
a popup window that displays additional content. This popup window will probably be interactive
and will probably be within an ASP.NET AJAX UpdatePanel, so it will be able to perform complex
server-based processing (including postbacks) without affecting the rest of the page. The popup
window can contain any content, including ASP.NET server controls, HTML elements, etc. Once the
work of the popup window is done, a simple server-side call dismisses it and triggers any relevant
script on the client to run and update the page dynamically.
The control above is initialized with this code. The italic properties are optional:
<ajaxToolkit:PopupControlExtender ID="PopEx" runat="server"