I was able to create a popup control extender with radio buttons for selecting logos in a GridView. The backend code was written in C# and used to populate the radio button list based on files in an image folder.

I was struggling to get a loading GIF to display when updating my ASP.NET UpdatePanel, but I finally found a solution that works for me. By using custom JavaScript handlers, I can now control the display of my loading GIF based on specific conditions.