title: Align right with center of panel using RelativePanel
body: <p>I want to align right of control with center of panel, how can I do that?</p>
  
  <p>Using column definitions does not work.</p>
  
  <blockquote>
    <p>RelativePanel error: The name 'MiddleSplitter' does not exist in the current context</p>
  </blockquote>
  
  <pre><code>&lt;Grid x:Name="LayoutRoot"&gt;
  
      &lt;Grid.ColumnDefinitions&gt;
          &lt;ColumnDefinition/&gt;
          &lt;ColumnDefinition x:Name="MiddleSplitter"/&gt; &lt;!--get middle?--&gt;
      &lt;/Grid.ColumnDefinitions&gt;
  
      &lt;VisualStateManager.VisualStateGroups&gt;
          &lt;VisualStateGroup&gt;
              &lt;VisualState&gt;
                  &lt;VisualState.StateTriggers&gt;
                      &lt;StateTrigger IsActive="True"/&gt; &lt;!--just for test--&gt;
                  &lt;/VisualState.StateTriggers&gt;
                  &lt;VisualState.Setters&gt;
  
                      &lt;Setter Target="AppListBox.(RelativePanel.AlignRightWith)" Value="MiddleSplitter"/&gt;
  
                  &lt;/VisualState.Setters&gt;
              &lt;/VisualState&gt;
          &lt;/VisualStateGroup&gt;
      &lt;/VisualStateManager.VisualStateGroups&gt;
  
      &lt;ScrollViewer Grid.ColumnSpan="2"&gt;
          &lt;RelativePanel Margin="5"&gt;
  
              &lt;ListBox Name="AppListBox" Height="150" Margin="5"/&gt;
  
          &lt;/RelativePanel&gt;
      &lt;/ScrollViewer&gt;
  &lt;/Grid&gt;
  </code></pre>
  
  <p>I <strong>have</strong> to use RelativePanel, this is simplified to only show the control that has this problem (<code>AppListBox</code>), I don't want to use other type of panels.</p>