Visual studio 2019 go to definition and Intellisense not working

Question

I have noticed a weird issue with Visual Studio 2019 v16.0.1 the IntelliSense about \"Using directive is unnecessary\" normally grey is missing and type reference suggestion

Answer 1

1. Close Visual Studio
2. Delete .vs folder (it is a hidden folder inside the folder which contains the solution *.sln)
3. Start Visual Studio

Solved my problem

NOTE 1: I am using Visual Studio 2019, but it may work on other versions
NOTE 2: This did not solve the OP problem, but it is a good candidate to solve your