title: Upgrading from VS2019 community to professional version got errro CS0579
body: <p>i have upgraded VS2019 community version to the professional version and I have developed a dynamic web site. now when I build the solution I get the following error:</p>
  <p>CS0579 Duplicate 'global::system.Runtime.Versioning.TargetFrameworkAttribute'</p>
  <p>plz guide as I am new to VS2019</p>
  <p>Regards</p>