Question : Visual Studio error: type exists in both the referenceassemblies and the GAC

After converting my web project over to VS 2010, I am now getting an error that several types (System.Web.Extensions.UpdatePanel for example) exist in both the GAC and the ReferenceAssemblies folder under Program Files. It looks like this is true, but how do I get around it? Why can't it just choose one and get on with it?!

Answer : Visual Studio error: type exists in both the referenceassemblies and the GAC

can you just try removiing it from referenced assemblies? clear the temp cache, temp internet files, and reset IIS, and then try it one more time.