title: "Predefined type 'System.*' is not defined or imported" Error, visual studio code, omnisharp
body: <p>I'm having an issue with the mentioned error in several .net core applications. I'm using vs code version 1.18.0 but the error started to appear already in the previous version.</p>
  
  <p>The error appears in every .cs file for every datatype like string, int, void etc. and also for class imports.</p>
  
  <p>All the projects still compile and run properly. Also on another workstation I'm <strong>not</strong> having the issue in the same projects, so it seems to be a local omnisharp/ vs code or windows? problem.</p>
  
  <p>Has anyone had something like this and managed to fix it or any suggestions on what i could try?</p>
  
  <p>I've reinstalled vs code and omnisharp already, but I'm still having the problem.</p>
  
  <p><strong>example Error:</strong>
  <em>Predefined type 'System.Object' is not defined or imported [GG]</em></p>