So you have used update panels before.  And the same code you may have used in an AJAX enabled website does not work when you put it into a Web Application.

I struggled with this for several hours before discovering that if you have the following line in your web.config file it breaks ASP.Net AJAX.

I have not researched the reason behind this but I plan to do so and will give an update when I find more information.  Just know that you can comment out this line or change the mode from Legacy and your Update Panel should […]