I've attached two screenshots, a before and after that displays my Visual Studio 2010 Design Views with the errors and the fixed result.
The part that helped me figure it out was with the RadScheduler. It displayed a much more helpful message that helped me find the solution.
If you notice in the "error" screen shot the RadTreeView and RadMenu controls do not display anything but the error message. But when I dragged a RadScheduler on the page, it displayed a much more helpful message.
Since I had just upgraded my ASP.NET AJAX controls to the latest version yesterday, the local cached version was still the prior version. This is what caused the errors.
So here's what I did:
- Close Visual Studio
- Navigate to the location of the older Telerik assembly
- Delete it
- Open Visual Studio - and everything works!
If you don't see a message that shows the path of the problem assembly, try dragging a RadScheduler onto the page to see if that shows the details paths.
Edit - 1/23/2012
This problem seemed to persist in later days, and I finally found a good work around. In your web.config, you need to change this...
... to this.
Remember to change the version number to the version you have installed in your application.
This works, but it does mean that you will have to manually update the version number if you ever upgrade your application in the future, but at least it will not generate all those errors.
If anyone has a better solution, I would love to hear it.
I hope this helps.