Visual Studio cannot identify ASP. NET's "asp" label prefix

Today, I encountered a strange phenomenon. My Visual Studio 2008 suddenly failed to recognize ASP. the "asp" label prefix in. Net initially thought it was a problem with Visual Studio. After the system was restarted, it still did not solve the problem. Then, in the "add and delete"ProgramThe problem still persists after Visual Studio is fixed. A Google search result is displayed on an msdn blog:

I blogged earlier that in VS 2005 we switched from using static XML Schemas to automatically generating them using reflection on Web controls. XML schemas are generated on demand as you open pages in your web site. they contain information about ASP. net controls, custom and user controls. you can find generated files cache in

C: \ Documents ents and Settings \ [username] \ Application Data \ Microsoft \ visualstudio \ 8.0 \ reflectedschemas

So, the first thing you want to do if you see dreaded "'asp 'is an unrecognized tag prefix or device filter" error is to close all vs instances and then delete the folder contents. restart vs, open your web site and we will generate schemas again.

Then IC: \ Documents ents and Settings \ [username] \ Application Data \ Microsoft \ visualstudio \ 9.0Delete (it's okay, Vs will be rebuilt) and start vs to open the project. Everything works.

Why does this happen? That's because I changed a Windows user and copied the application data from the old user. Vs may not be able to recognize the content under reflectedschemas, therefore, the prefixes of all "asp" labels cannot be identified.