title: .NET Standard 2.0 cannot be referenced in .NET Framework 2.0
body: <p>I received an error:</p>
  
  <p>'c:......\xxxx.csproj' targets '.NETStandard,Version=v2.0'. It cannot be referenced by a project that targets '.NETFramework,Version=v2.0'.   WindowsFormsApp1            </p>
  
  <p>How to resolve?</p>