title: How can I pass data from an aspx page to an ascx modal popup?
body: <p>I'm fairly new to ASP.NET and trying to learn how things are done. I come from a C# background so the code-behind portion is easy, but thinking like a web developer is unfamiliar.</p>
  
  <p>I have an aspx page that contains a grid of checkboxes. I have a button that is coded via a Button_Click event to collect a list of which rows are checked and create a session variable out of that list. The same button is referenced (via TargetControlID) by my ascx page's ModalPopupExtender which controls the panel on the ascx page.</p>
  
  <p>When the button is clicked, the modal popup opens but the Button_Click event is never fired, so the modal doesn't get its session data.</p>
  
  <p>Since the two pages are separate, I can't call the ModalPopupExtender from the aspx.cs code, I can't reach the list of checkboxes from the ascx.cs code, and I don't see a way to populate my session variable and then programmatically activate some other hidden button or control which will then open my modal popup.</p>
  
  <p>Any thoughts?</p>