title: What is the difference between Task<> and IAsyncOperation<>
body: <p>I am writing a metro app.</p>
  
  <p>This works:</p>
  
  <pre><code>    HttpClient client = new HttpClient();
      var bytes = await client.GetByteArrayAsync(new Uri("www.microsoft.com"));
  </code></pre>
  
  <p>This doesn't:</p>
  
  <pre><code>    var folder = Windows.Storage.ApplicationData.Current.LocalFolder;
      var file = await folder.GetFileAsync("text.txt");
  </code></pre>
  
  <p>The first one returns a Task&lt;>, the second one return an IAsyncOperation&lt;></p>
  
  <p>What is the difference? Why are there two different types? How can I fix the second sample?</p>