title: The current .NET SDK does not support targeting .NET Core 3.1
body: <p>I have downloaded and install Visual Studio 2019 and have dotnet core 3.1 installed.
  As I am starting to play around with VS, I have just created a simple project using VS built-in Web App Template and try to run without debugging.</p>
  
  <p>It gives the error of "The current .NET SDK does not support targeting .NET Core 3.1.  Either target .NET Core 3.0 or lower, or use a version of the .NET SDK that supports .NET Core 3.1."</p>
  
  <p>May I know how it can be resolved?</p>
  
  <p>Thanks.</p>
  
  <p>Regards,
  Andrew</p>