title: WP7 Toolkit PerformanceProgresBar and UI thread (losing dots effect)
body: <p>I have a very hard time managing the ProgressBar from WP Toolkit.
  In my project I have a listbox populated with databound items. 
  The population process goes like this:</p>
  
  <ol>
  <li>show progress bar (visibility changed to visible, IsIndeterminate to true),</li>
  <li>make a rest request,</li>
  <li>get a response,</li>
  <li>parse a collection of items,</li>
  <li>bind items in memory to list,</li>
  <li>hide progress bar (visibility to collapsed, IsIndeterminate to false).</li>
  </ol>
  
  <p>My problem now is:
  The Indeterminate flag seems to change too fast (different threads i think?). This causes the progress bar to display sometimes only one rectangle. 
  How can I ensure that the progress bar will dissapear only after databinding and listbox refreshing is complete?</p>
  
  <p>Here is my response callback:</p>
  
  <pre><code>private void DataLoaded(object o, RestResponseEventArgs e)
  {   
    int i = 0;
    List&lt;Entry&gt; entries = new List&lt;Entry&gt;();
    foreach (JObject current in e.JsonObject["entries"].Children())
    {
       Entry e = Entry.Parse(current);
       entries.Add(e);
    }
    this.MyListBox.ItemsSource = entries;
    this.ProgressBar.Visibility = Visibility.Collapsed;
    this.ProgressBar.IsIndeterminate = false;
  }
  </code></pre>