title: WPF Material Design Progress Dialog not shown during a task execution
body: <p>I try to open a material design dialog while some task is executed in the background. Therefore, I wrapped my DockPanel with the DialogHost <code>&lt;materialDesign:DialogHost&gt;</code> and overloaded the the <code>Show</code> method with the callback delegates.</p>
  
  <p>When I click a Button, a progress dialog during the task execution shoud be shown, e.g.</p>
  
  <pre><code>private async void LoadConfigButton_Click(object sender, RoutedEventArgs e)
  {
              var dialogContent = new TextBlock
              {
                  Text = "Loading.... Please wait.",
                  Margin = new Thickness(20)
              };
              await DialogHost.Show(dialogContent,
                  new DialogOpenedEventHandler((object senderDialog, DialogOpenedEventArgs args) =&gt;
                  {
                  // DoStuffMethod();
                  }));
  
  }
  </code></pre>
  
  <p>Now, I see the progress dialog, but only after the <code>"Do stuff method"</code> has been completed. </p>
  
  <p>What am I missing here?</p>