Ran into an issue using a jQuery.UI.Dialog control on an asp.net web form today. When defining a dialog jQuery.UI takes the dialog and appends it right before the closing </body> tag. This is outside of the <form> tag causing any values you wanted from the form to be empty in your code-behind.
Here is the fix that worked for me:
This works great and the dialog now displays as expected, capturing the results in the code behind except for I originally wanted the dialog wrapped in a UpdatePanel. In order to fix this issue, I created an empty div and appended the dialog content there:
Not the results i expected. When the content refreshes the dialog is messed up. The answer was to move the content panel inside of the dialog with the user control doing all the work!!!
<div id="dialog" class="ui-widget-content ui-corner-all" title="Add New Client"></div>