Archives / 2010 / August
  • How to fix "Validation(): Element 'xxxx' is not supported" and "Unrecognized tag prefix or device filter 'asp'"

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

    Unrecognized tag prefix or device filter 'asp'
    Validation(): Element 'Label' is not supported.
    Validation(): Element 'GridView' is not supported

    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 Visual studio ,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 this article on Doug Kennard's blog:

    Splendid,that article is a life savior,the idea is to remove the folder "ReflectedSchemas" from paths:

    Win XP : C:\Documents and Settings\{username}\Application Data\Microsoft\VisualStudio\10.0\ReflectedSchemas

    Win Vista / 7: C:\Users\{username}\AppData\Roaming \Microsoft\VisualStudio\10.0\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 any Visual studio version,keep in mind that you have to use the correct VS version number i.e

    Visual studio 2010 : %appdata%\Microsoft\VisualStudio\10.0\ReflectedSchemas
    Visual studio 2012: %appdata%\Microsoft\\VisualStudio\11.0\ReflectedSchemas
    Visual studio 2013: %appdata%\Microsoft\VisualStudio\12.0\ReflectedSchemas

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