title: 'HttpContext' could not be found on Linux
body: <p>Linux, .Net Core 2.2.105, VS Code.</p>
  
  <p>I've done 'dotnet new webapi', and trying to add a class which inherits HttpContext, however VS Code complains</p>
  
  <blockquote>
    <p>The type or namespace name 'HttpContext' could not be found</p>
  </blockquote>
  
  <p>I have using 'System.Web;' at the top, my projects.assets.json has </p>
  
  <blockquote>
    <p>"ref/netcoreapp2.2/System.Web.dll": {},</p>
  </blockquote>
  
  <p>What am I missing?</p>