title: Grid inside Scrollview not scrolling by mouse wheel
body: <p>I have a column in a grid which contains 3 <code>GroupBoxe</code>s. The last <code>GroupBox</code> has a <code>Grid</code> containing two elements: a <code>Button</code> and a <code>TreeView</code> (vertical). The <code>TreeView</code> should have a dynamically height because it contains elements which can be expanded/collapsed.</p>
  
  <p>The window which contais all elements can be resized by the user. </p>
  
  <p>If the window is to small you can't see all groupboxes so I need a Scrollbar. I can scroll down but if I want to scroll inside the <code>TreeView</code> by the mouse wheel nothing happens.</p>
  
  <p>This is my code:</p>
  
  <p></p>
  
  <pre><code>&lt;Grid&gt;
      &lt;Grid.ColumnDefinitions&gt;
          &lt;ColumnDefinition Width="*" /&gt;
      &lt;/Grid.ColumnDefinitions&gt;
      &lt;Grid.RowDefinitions&gt;
          &lt;RowDefinition Height="Auto"/&gt;
          &lt;RowDefinition Height="Auto"/&gt;
          &lt;RowDefinition Height="*"/&gt;
      &lt;/Grid.RowDefinitions&gt;
  
      &lt;GroupBox Header="Test 1" Grid.Row="0"&gt;...&lt;/GroupBox&gt;
  
      &lt;GroupBox Header="Test 2" Grid.Row="1"&gt;...&lt;/GroupBox&gt;
  
      &lt;GroupBox Header="Test 3" Grid.Row="2"&gt;
  
          &lt;Grid&gt;
              &lt;Grid.RowDefinitions&gt;
                  &lt;RowDefinition Height="Auto"/&gt;
                  &lt;RowDefinition Height="*"/&gt;
              &lt;/Grid.RowDefinitions&gt;
  
              &lt;CheckBox Content="All" Grid.Row="0"/&gt;
  
              &lt;TreeView x:Name="NameTree" 
                  Grid.Row="1"
                  ItemsSource="{Binding Names}"/&gt;
          &lt;/Grid&gt;
  
      &lt;/GroupBox&gt;
  
  &lt;/Grid&gt;
  </code></pre>
  
  <p></p>
  
  <p>A workaround could be to set the 3rd row to a fixed size instead of using the *. In this case I will two scrollbars (the ScrollViewer and the TreeViews Scrollbar, but I want a dynamically height of the 3rd groupbox. </p>