title: Using async / await in .NET Portable Library project
body: <p>This line </p>
  
  <pre><code>StorageFile photo = await cameraUI.CaptureFileAsync(CameraCaptureUIMode.Photo);
  </code></pre>
  
  <p>gives me this error:</p>
  
  <blockquote>
    <p>Error CS0012<br>
    The type 'IAsyncOperation&lt;>' is defined in an assembly
    that is not referenced. You must add a reference to assembly
    'Windows.Foundation.FoundationContract, Version=3.0.0.0,
    Culture=neutral,</p>
  </blockquote>
  
  <p>How to fix it?  </p>
  
  <p><a href="https://i.stack.imgur.com/VCsGM.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/VCsGM.png" alt="screenshot"></a></p>