This exact thing happened to me. Do you have ReSharper? If so, the solution I found here may work for you. From Alexander’s comment in the accepted answer:
Try cleaning R# caches C:\Users{User
Name}\AppData\Local\JetBrains\ReSharper\v8.2\SolutionCaches\ and then
reopen the solution
From below comment – that’s %userprofile%\AppData\Local\JetBrains\ReSharper\v8.2\SolutionCaches for those that want to Win+R.
From comment below, another possible location:
%userprofile%\AppData\Local\JetBrains\Transient\ReSharperPlatformVs12\v02\SolutionCaches
Update – Another Easier Option:
You can also go to ReSharper option, Environment/General, click on Clear Caches and restart Visual Studio – Chin Feb 27 at 2:02
