This blog post has been updated !!!
If you tried our Q1 2009 Beta you have probably noticed that there is a brand new assembly installed in your GAC - Telerik.Web.Design.dll. We decided to separate the design-time code from the web control implementation code. The reasons are many - better separation of concerns, less assembly references for the main assembly (Telerik.Web.UI.dll). We now have the freedom to extend the design time capabilities of RadControls for ASP.NET Ajax without bloating the main control assembly.
Why didn't we make it that way from the beginning? The only reason is that Visual Studio 2008 had a problem with loading GAC-ed design-time assemblies of control libraries deployed in the BIN folder of a web site. Strangely enough the problem didn't appear in Visual Studio 2005. The good news is that this bug has been fixed in Visual Studio 2008 SP1!
However if you for some reason cannot upgrade to Visual Studio 2008 SP1 you will face the following exception after upgrading to RadControls for ASP.NET Ajax Q1 2009:
Fortunately there are three ways to solve this problem (apart from the obvious upgrade to Visual Studio 2008 SP1):
I hope this helps.
Atanas Korchev is Team Leader in Kendo UI Team