got error " The "RazorGenerate" task failed unexpectedly. " .After Updating to VS 16.8 and upgrade to .net 5.. the core version target is Core 2.2

The fix for me was to introduce a new System Environment Variable with the Key "DOTNET_HOST_PATH" and the value "dotnet" and then to restart Visual Studio.

I did 3 steps to get it to build AND to get the ( ~/ ) variable to work.

1. Open cmd and write this: setx DOTNET_HOST_PATH "%ProgramFiles%\dotnet\dotnet.exe"
2. Open C:\Program Files\dotnet\sdk in here delete the folder: NuGetFallbackFolder
3. Restart your pc!

It worked on the build server, after I added this Nuget package:

Microsoft.NET.Sdk.Razor

Since I added the Net.SDK.Razor package, it builds successfully.

I had also added Microsoft.AspNetCore.Razor.Design, but only Microsoft.NET.Sdk.Razor is actually needed.