title: CSC on macos does not list C# 9
body: <p>I have updated to the latest .NET 5 SDK 5.0.101 but it seems the CSC compiler is unaware of the existence of C# 9. I have tried using C# 9 features (like init-setters) in Visual Studio Code and Visual Studio Mac (also in Rider), and they work, so I know C# 9 is there. However if I run &quot;csc -langversion:?&quot; it only lists up to 8.0. If I explicitly try to set the langversion to 9.0 (or just &quot;9&quot;) I get an error like:
  <code>Invalid option '9.0' for /langversion. Use '/langversion:?' to list supported values</code></p>
  <p>So I'm wondering if my environment might not be configured correctly. I mean, things seem to be working but I'm a bit confused about the missing lang-version in the output, and wondering if this may indicate some issue with my current install. Any suggestions?</p>
  <p>I'm running macos 10.15.7 (Catalina) and as mentioned above have the latest .NET SDK installed.</p>