Visual Studio 2015 not syntax highlighting razor nor Intellisense

I had the same problem, the only fix so far is by resetting all user data (C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\IDE\devenv.exe /ResetUserData).

NOTE: You will lose all customizations, e.g. keyboard shortcuts and window layouts if you do this!

EDIT: People are saying this only works for RC, not RTM, so you might want to try the other fixes first.

I had the same problem in VS 2015 RTM and was able to fix it by simply loading Visual Studio in Safe Mode by:

C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\IDE\devenv.exe /SafeMode

then closing and reopening it normally.

I've found in this answer another way to fix it without the devenv.exe /ResetUserData

Just delete the contents of this directory with Visual Studio closed: %LocalAppData%\Microsoft\VisualStudio\<visual_studio_version_number>\ComponentModelCache

To find the version number of the Visual Studio edition your are running please refer this list. Note that only the major number is important, the minor version can and will probably differ. In my case I had Visual Studio 2017 Enterprise installed so I looked for 15.xx and found 15.0_9a1c4a06 inside the AppData folder.