How to solve the error "Must use PackageReference"?
VS2017/VS2019 -> Solution Explorer -> right-click References -> "Migrate packages.config to PackageReference"
VS2019 -> Solution Explorer -> right-click packages.config -> "Migrate packages.config to PackageReference"
Solution that worked for me was to:
- Run a Clean on the project in question
- Close Visual Studio
- Navigate to the project folder on disk and delete the obj folder
- Reopen Visual Studio and Build