title: How to add all missing usings at once with Visual Studio 2019 and C#
body: <p>When I write C#, I sometimes have 3-4 missing usings which I can add with the tooltip window -> add missing using, or doing ctrl + . On the line where a missing using is present.</p>
  
  <p>Doing this 3-4 times is rather annoying.</p>
  
  <p>I have noticed a "add all missing usings" tooltip sometimes, which worked, but I can not get it to pop up reliably. </p>
  
  <p>I know resharper has it, but I don't want to use a paid extension for this feature.</p>
  
  <p>How can I reliably get this "add all missing usings" pop up, or in what other way can I add all missing usings at once?</p>
  
  <p>Thanks!</p>