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Editable ComboBox Keyboard Navigation Issues

• Thursday, November 05, 2009 3:40 PMbmeardon

   
  

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  It appears as if there is a defect in the WPF ComboBox control pertaining to keyboard navigation (tab) behavior when the ComboBox.IsEditable property is set to true.  Consider the following simple example:
  
  

  <Window x:Class="KeyboardNavProto.MainWindow"
  
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  
      Title="Keyboard Navigation Prototype" Height="156" Width="378">
  
      <WrapPanel>
  
          <ComboBox SelectedIndex="0" IsEditable="True">
  
              <ComboBoxItem Content="A" />
  
              <ComboBoxItem Content="B" />
  
              <ComboBoxItem Content="C" />
  
          </ComboBox>
  
          <ComboBox SelectedIndex="0" IsEditable="True" IsTabStop="False">
  
              <ComboBoxItem Content="A" />
  
              <ComboBoxItem Content="B" />
  
              <ComboBoxItem Content="C" />
  
          </ComboBox>
  
          <ComboBox SelectedIndex="0" IsEditable="True">
  
              <ComboBoxItem Content="A" />
  
              <ComboBoxItem Content="B" />
  
              <ComboBoxItem Content="C" />
  
          </ComboBox>
  
      </WrapPanel>
  
  </Window>
  
  

  
  You would expect for the second ComboBox (whose IsTabStop=false) to be skipped, but it is not.  You can tab forward and backwards (shift+tab) to it, even though it should no longer be participating in the tab order.  An addtional quirk is if an editable ComboBox's IsTabStop is explicitly set to true as show below:
  
  

          <ComboBox SelectedIndex="0" IsEditable="True" IsTabStop="True">
              <ComboBoxItem Content="A" />
              <ComboBoxItem Content="B" />
              <ComboBoxItem Content="C" />
          </ComboBox>
  

  
  You can tab forward to the ComboBox, forward tab out of it to the next control, but you can't backward tab (shift+tab) out of it to the previous control.
  
  I've gone as far as replacing the ComboBox's control template, but even this doesn't seem to solve the issues, which seem to be intrinsic to the ComboBox control implementation.
  
  I verified this problem in .NET 3.5 SP1, and .NET 4.0 Beta 2.
  
  None of these issues seem to apply to a non-editable ComboBox, which behaves as expected in regards to the setting of the IsTabStop property.
  
  We have a need to have our ComboBoxes editable, but would like to remove some of those editable ComboBoxes from the tab order.  We have found other workarounds (like responding to when they've been entered and forcing the keyboard focus to the next control in an event handler), but would like to know if this is a recoginzed issue and when/if it will be fixed.
  
  Thanks,
  Brandon
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