title: ToolStripComboBox.SelectedItem change does not propagate to binding source
body: <p>My binding is set up as this:</p>
  
  <pre><code>        _selectXAxisUnitViewModelBindingSource = new BindingSource();
          _selectXAxisUnitViewModelBindingSource.DataSource = typeof(SelectXAxisUnitViewModel);
  
          _selectedUnitComboBoxBindingSource = new BindingSource();
          _selectedUnitComboBoxBindingSource.DataSource = _selectXAxisUnitViewModelBindingSource;
          _selectedUnitComboBoxBindingSource.DataMember = "AvailableUnits";
  
          _selectedUnitComboBox.ComboBox.DataSource = _selectedUnitComboBoxBindingSource;
          _selectedUnitComboBox.ComboBox.DisplayMember = String.Empty;
          _selectedUnitComboBox.ComboBox.ValueMember = String.Empty;
          _selectedUnitComboBox.ComboBox.DataBindings.Add("SelectedItem",
                                                          _selectXAxisUnitViewModelBindingSource, 
                                                          "SelectedUnit", true, DataSourceUpdateMode.OnPropertyChanged);
  
          // this is a bug in the .Net framework: http://connect.microsoft.com/VisualStudio/feedback/details/473777/toolstripcombobox-nested-on-toolstripdropdownbutton-not-getting-bindingcontext
          _selectedUnitComboBox.ComboBox.BindingContext = this.BindingContext;
  </code></pre>
  
  <p>The property "AvailableUnits" is a collection of strings and the "SelectedUnit" is a string-property. Now the dropdown list is populated as expected, but when I select and item in the list, the change is not propagated to the binding source. Any idea what I am doing wrong?</p>
  
  <p>Update:</p>
  
  <p>I Created a little test project and this problem occurs when I add a ToolStripComboBox as a subitem of another ToolStripItem. If I add the ToolStripItem directly to the MenuStrip everything works fine. The BindingContext is not assigned to the ToolStripComboBox when added as a sub item (see my code-comment) and my fix doesn't seem to do whats necessary to get this to work.</p>