title: Xamarin.Forms.Platform.Android does not exist after Xamarin update from 2.5 to 3.5
body: <p>I have updated my projects Xamarin.Forms NuGet package from version 2.5 to 3.5. After this update I got an error in my Android project saying:</p>
  
  <blockquote>
    <p>The type or namespace name 'Android' does not exist in the namespace
    'Xamarin.Forms.Platform' (are you missing an assembly reference?)</p>
  </blockquote>
  
  <p>What I've tried so far:</p>
  
  <ul>
  <li>Delete bin, obj folders</li>
  <li>Close and Reopen solution</li>
  <li>Clean and Rebuild solution</li>
  <li>Reinstalling Xamarin Forms NuGet</li>
  </ul>