title: Open file in existing instance of Visual Studio 2017
body: <p>I used to be able to open a file in an existing instance of VS - <code>devenv.exe</code> had a <code>/dde</code> switch for that.</p>
  
  <p>But with VS2017 it opens the file in a new instance, not the one already running.</p>
  
  <p>For example for json files:</p>
  
  <ul>
  <li>My registry has a key <code>HKEY_CLASSES_ROOT\.json\OpenWithProgids</code> which contains a value <code>VisualStudio.json</code>.</li>
  <li>And there is a key <code>HKEY_CLASSES_ROOT\VisualStudio.json\shell\Open\Command</code> which contains the default value <code>"C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\Common7\IDE\devenv.exe" /dde</code>.</li>
  </ul>
  
  <p>But that <code>/dde</code> is ignored.</p>
  
  <p>Maybe all the betas and RCs corrupted something. My VS2017 is the latest updated version.</p>
  
  <p>Does the <code>/dde</code> switch still work?</p>