Ok, so, my visual studio is broken. I say this NOT prematurely, as it was my first response to see where I had messed up in my code. When I add controls to the page I can\'t
In my case, I was working with some old web site code, which I converted to a VS2008 solution. I encountered this same problem.
For me, the fix was to right-click the Web Sites project in the Solution Explorer and select Convert to Web Application. This created designer.cs files for all pages, which did not yet have these files before.