This fixed my razor intellisense problem and the error after installing the latest ASP.NET tools.
Here is how to fix it.
Delete the contents from the following folders:
C:\Users{user}\AppData\Local\Microsoft\VisualStudio
C:\Users{user}\AppData\Local\Microsoft\VSCommon
Navigate to the command line now and run devenv from either of these paths:
[x64] C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\IDE
[x86] C:\Program Files\Microsoft Visual Studio 14.0\Common7\IDE
run devenv /resetuserdata from the command prompt.
Thanks to fka for the steps!
https://stackoverflow.com/questions/34084003/visual-studio-2015-error-object-reference-not-set-to-an-instance-of-an-object/34085345#34085345
Happy Coding!