ASP.NET AJAX Cascading Dropdowns – Method error 500

Another one almost driving me crazy. After about 8 hours of digging around I finally found a post that helped:

http://forums.asp.net/thread/1486888.aspx

The problem I was having, like many others, was this: I was trying to implement two cascading dropdown lists using ASP.NET AJAX (following this AJAX video – scroll down to #3 How Do I: Use the ASP.NET AJAX CascadingDropDown Control Extender?) . Everything worked except the second dropdown wouldn’t be filled with values but with error code: Method error 500.

Following the hints in the post help me nail it down. It seems the beta releases of ASP.NET AJAX have been extremely buggy. Many of the posts I found were from this beta period, which creates nightmares when you’re trying to find a solution to your problem. Great feeling when you finally nails it!

Like the video I used an XML file as data store. This is a very simple and fast implementation for small applications. If you want to use a database instead there are some sites that give some guidelines but unfortunely no one gives the whole story. This and this are the best places to start. Also this one contains lots of good info but i was having problems following along in his discussions.