How to fix "Validation(): Element 'xxxx' is not supported

How to fix "Validation(): Element 'xxxx' is not supported" Visual Studio 2010

Introduction:

Since about a month ago,I started to get validation warnings at design time on asp.net server controls (any control actually) within the html design view for VS 2010,intellisense on all controls would not work at all,the messages look like this:

Validation(): Element 'Label' is not supported.
Validation(): Element 'GridView' is not supported
....etc

The compilation done successfully but the warnings still exist and intellisense is not working at the source tab

I tried to reset the settings of VS 2010 ,disabled all extensions and few other ideas but none of them solved the issue,I got stuck.

I did a search over the internet about this issue and found the Solution

Solution

Splendid,that article is a life savior,the idea is to remove the folder "ReflectedSchemas" from paths:
Remember also the "VisualStudio" part of the path will be different depending on the version installed.

Win XP : C:\Documents and Settings\{username}\Application Data\Microsoft\VisualStudio\9.0\ReflectedSchemas

Win 7: C:\Users\{username}\AppData\Roaming \Microsoft\VisualStudio\9.0\ReflectedSchemas

 

Note: make sure that "Show hidden files, folders, and drives" is selected from Folder Options ,also don't forget to close VS before deleting the folder.

This solution should work for VS2010 and VS2008,at VS2008 you have to delete ReflectedSchemas from folder 9.0 not 10.0.