ViewModel breaks UI automation in WPF

Question

Hi,

I have a WPF application that mostly follows MVVM, which I am trying to automate.

In some of my user controls I bind the Content property to the ViewModel of another user control. There is a data template defined which maps the ViewModel to the correct View to show on the screen.

This works fine for when the application is run by a user, but if I try to view the automation tree in UISpy or another tool, it always stops at the ViewModel.

I have found this problem in numerous places. Is there a way to tell the ViewModel to expose any automation properties beneath it in the tree? or am I defining the data template wrong?

Thanks in advance, Donal

EDIT: Here is a sample XAML taken from the app. It is blocking accessing the automation tree. It is placed inside a RibbonWindow.

<TabControl Grid.Column="2" 
   cal:RegionManager.RegionName="{x:Static Regions:RegionNames.MainRegion}"  
   Name="tabControlMain" 
   SelectedValuePath="Name">
       <TabControl.Template>
          <ControlTemplate TargetType="TabControl">
              <Grid>
                <TabPanel IsItemsHost="True" Visibility="Hidden" />
                <Border BorderBrush="{DynamicResource BorderBrush}" Background="White" BorderThickness="1">
                    <framework:CachingContentPresenter 
                        ItemsSource="{Binding Items, ElementName=tabControlMain}" 
                        ContentTemplateSelector="{framework:MvvmTemplateSelector}"
                        ContentSource="SelectedContent" />
                </Border>
              </Grid>
          </ControlTemplate>
     </TabControl.Template>

Below is a previous version of the above XAML. It was allowing access to the automation tree:

<TabControl 
     Grid.Column="2" 
     Padding="0" 
     cal:RegionManager.RegionName="{x:Static Regions:RegionNames.MainRegion}"  
     Name="tabControlMain" 
     TabStripPlacement="Bottom" 
     SelectedValuePath="Name" 
     ItemContainerStyle="{StaticResource TabItemStyle}">
</TabControl>

Where the TabItemStyle is:

<Style TargetType="{x:Type TabItem}" x:Key="TabItemStyle">
   <Setter Property="Template">
      <Setter.Value>
          <ControlTemplate TargetType="TabItem">
          </ControlTemplate>
      </Setter.Value>
   </Setter>
</Style>

Answer 1

Hi,

I managed to find a solution to the XAML posted above. I'm not sure if it will work in all cases in our app, but I have yet to try them properly.

Anyway, the fix was found in this post: http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/fa8eb86f-5001-4af6-adb3-ceb0799a0cf3/

Basically, we added 'Name="PART_SelectedContentHost"' to the CachingContentPresenter in the ControlTemplate. From my understanding, this PART_ tells the parser/compiler to include the default behaviour of the control template such as mouse events and keyboard presses as well as Automation properties.