title: Exception using await HttpClient.GetAsync in Portable Class Library
body: <p>I have Portable Class Library(net40+sl4+win8+wp71) with code:<br>
  </p>
  
  <pre><code>    public static async Task&lt;Dictionary&lt;string, FeedItem&gt;&gt; GetFeeds()  
      {  
          try
          {
              string data;
              using (HttpMessageHandler handler = new HttpClientHandler())
              {
                  using (HttpClient httpClient = new HttpClient(handler))
                  {
                      data = await httpClient.GetStringAsync(FeedsUrl + Guid.NewGuid()).ConfigureAwait(false);
                  }
              }
  
              if (data != null)
              {
                  //...
              }
              return null;
          }
          catch
          {
              return null;
          }
      }
  </code></pre>
  
  <p>Microsoft.Bcl, Microsoft.Bcl.Async and Microsoft.Net.Http are referenced.</p>
  
  <p>I use this library in Windows 8 Metro app. Then I debugg app through VS2012, it is ok. But when I create App Package and install it, the app crashes on first launch everytime with error:</p>
  
  <pre><code>Framework Version: v4.0.30319
  Description: The process was terminated due to an unhandled exception.
  Exception Info: System.Runtime.InteropServices.COMException
  Stack:
     at System.Runtime.CompilerServices.AsyncMethodBuilderCore.&lt;ThrowAsync&gt;b__1(System.Object)
     at System.Threading.QueueUserWorkItemCallback.WaitCallback_Context(System.Object)
     at System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)
     at System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)
     at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
     at System.Threading.ThreadPoolWorkQueue.Dispatch()
     at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()
  </code></pre>
  
  <p>Edit: If I comment line "data = await httpClient.GetStringAsync" it will work without exception.  </p>
  
  <p>On second launch it always works.  </p>
  
  <p>Any suggestion?</p>