VSCode .Net Core MVC reports problems but Project Builds and Runs just fine

Question

I have been using VSCode on OSX to develop a .Net Core Web MVC app. I can build and run the app using dotnet build cmd. No errors are reported when built. But today I opened VSCode and I am getting 100's of VSCode Problems reported by the C# extension. I can't figure out how to reset or solve this issue.

UPDATE: I created a new .Net Core MVC project using dotnet new mvc. I opened the project in vscode with no modifications. VSCode immediately showed the errors/problems. I opened this new project in VSCode on Windows. No errors. On VSCode OSX I removed the C# extension and the errors disappeared. I reinstalled the C# extension and the errors returned.

Answer 1

Set

{    
  "omnisharp.useGlobalMono": "never"
}

https://github.com/OmniSharp/omnisharp-vscode/issues/4134#issuecomment-714326240

Answer 2

If you have just installed something try to restart your PC.