An assembly specified in the application dependencies manifest (PortableAntiqities.deps.json) has already been found but with a different file extension

_From @Madmorgan007 on Friday, February 28, 2020 3:10:24 PM_

Hi,
I'm using Visual Studio 2019, Dotnet core 3.1 all updates are installed. Getting the following issue.
this issue happens when creating a controller or view.

Error:
An assembly specified in the application dependencies manifest (PortableAntiqities.deps.json) has already been found but with a different file extension:
package: 'Microsoft.VisualStudio.Web.CodeGeneration.Design', version: '3.1.1'
path: 'lib/net461/dotnet-aspnet-codegenerator-design.exe'
previously found assembly: 'C:\Users\Administrator\.nuget\packages\microsoft.visualstudio.web.codegeneration.design\3.1.1\lib\netcoreapp3.1\dotnet-aspnet-codegenerator-design.dll'

_Copied from original issue: dotnet/aspnetcore#19447_