title: WPF DataGridComboBoxColumn not showing the context menu?
body: <p>I am trying to make a DataGridComboBoxColumn that has a static list to choose from:  Not Started, In Progress, Completed</p>
  
  <p>Here is what I have in the XAML and while it builds fine I cannot see the options in the drop down: </p>
  
  <pre><code>           &lt;DataGridComboBoxColumn  Header="Status" Width="auto"  IsReadOnly="False"  &gt;
                  &lt;DataGridColumn.HeaderStyle&gt;
                      &lt;Style TargetType="DataGridColumnHeader"&gt;
                          &lt;Setter Property="Background" Value="LightGoldenrodYellow" /&gt;
                          &lt;Setter Property="BorderThickness" Value="2,2,0,2" /&gt;
                      &lt;/Style&gt;
  
                  &lt;/DataGridColumn.HeaderStyle&gt;
                  &lt;ContextMenuService.ContextMenu&gt;
                      &lt;ContextMenu&gt;
                          &lt;MenuItem Header="Not Started" /&gt;
                          &lt;MenuItem Header="In Progress"  /&gt;
                          &lt;MenuItem Header="Completed" /&gt;  
                      &lt;/ContextMenu&gt;
                  &lt;/ContextMenuService.ContextMenu&gt;
              &lt;/DataGridComboBoxColumn&gt;
  </code></pre>
  
  <p>I don't understand why this doesn't work they way that other DataGrid.ContextMenu's work.  I feel like I'm missing something really easy here.</p>