title: WPF Expander - when GridSplitter used to manually resize row, row does not properly collapse
body: <p>This is what I have</p>
  
  <pre><code>   &lt;Grid.RowDefinitions&gt;
        &lt;RowDefinition Height="Auto" MinHeight="25"/&gt;
        &lt;RowDefinition Height="Auto"/&gt;
        &lt;RowDefinition /&gt;
    &lt;/Grid.RowDefinitions&gt;
  
  &lt;Expander IsExpanded="False" Grid.Row="0" &gt;
       &lt;DataGrid name="FirstGrid" /&gt;
  &lt;/Expander&gt;
  &lt;GridSplitter Grid.Row="1" HorizontalAlignment="Stretch"  Height="5" /&gt;
  &lt;DataGrid Grid.Row="2" name="SecondGrid" /&gt;
  </code></pre>
  
  <p>When I click the expand button on the expander it correctly expands row 0 to the size of the DataGrid FirstGrid and it properly collapses the row as well. This does not work however if I expand the FirstGrid then manually resize that row by dragging the GridSplitter up or down and then pressing collapse button on the expander. What happens is that FirstGrid collapses but the row itself the FirstGrid is in does not. Any suggestions?</p>
  
  <p>Thanks</p>