title: Dividing WPF window
body: <p>I want to divide my window (wpf) in three columns: left column must be <code>DockPanel</code> ( I think <code>StackPanel</code> will not work on <code>Canvas</code>), the right column should be another <code>DockPanel</code> holding a <code>listbox</code> and in the middle I need to have a <code>Canvas</code>.</p>
  
  <p>This is what I have done and I am having problem with left column since it is not expandable. I need the left column as holder of custom object so that user could drag/drop them on canvas. Please advise.</p>
  
  <pre><code>&lt;DockPanel LastChildFill="True" Background="LightGray" Margin="5"&gt;
     &lt;Expander Header="Controls" Background="Gray" Margin="2" 
               Content="{StaticResource FC}" DockPanel.Dock="Top" 
               IsExpanded="True" Width="200" /&gt;
  &lt;/DockPanel&gt;
  
  &lt;GridSplitter Focusable="False" Width="2" Background="LightGray"
                VerticalAlignment="Stretch" HorizontalAlignment="Right"/&gt;
  
  &lt;lib:MyCanvas x:Name="myCanvas" FlowDirection="LeftToRight"  
           Background="White" AllowDrop="True" 
           Mouse.MouseMove="MyCanvas _MouseMove"&gt;
  &lt;/lib:MyCanvas &gt;
  </code></pre>
  
  <p>Also, what control should be used on the right side so that can hold a listbox?      </p>