I have an ASP.NET page using the AJAX library. There is a dropdownlist inside an UpdatePanel, which on index changing is supposed to update a different UpdatePanel to modify a grid control.

But after the page first comes up, and you adjust the ddl, the entire page postbacks, followed by a (correct) partial postback. After this one time, every other usage of the ddl performs correctly, trigger partial postbacks.

Both the panel and the ddl are being added from code. The UP is Conditional updates and ChildrenAsTriggers = true. The dropdownlist is AutoPostBack true and has an event set up on SelectedIndexChanged.

So what is going on? I've tried adjusting every setting I can think of and still the page completely refreshes once, then works fine after that.