NullReferenceException in System.Windows.Automation.Peers.GroupItemAutomationPeer.GetChildrenCore()

NullReferenceException in System.Windows.Automation.Peers.GroupItemAutomationPeer.GetChildrenCore() by AChisholm

Closed

as Fixed

Type:	Bug
ID:	316681
Opened:	12/10/2007 3:29:16 PM
Access Restriction:	Public

Workaround(s)

view

User(s) can reproduce this bug

On certain machines when running our WPF application it crashes with the following.

Exception:
Object reference not set to an instance of an object.

Stack Trace:
at System.Windows.Automation.Peers.GroupItemAutomationPeer.GetChildrenCore()
at System.Windows.Automation.Peers.AutomationPeer.EnsureChildren()
at System.Windows.Automation.Peers.AutomationPeer.UpdateChildren()
at System.Windows.Automation.Peers.AutomationPeer.UpdateSubtree()
at System.Windows.Automation.Peers.AutomationPeer.UpdateSubtree()
at System.Windows.Automation.Peers.AutomationPeer.UpdateSubtree()
at System.Windows.Automation.Peers.AutomationPeer.UpdateSubtree()
at System.Windows.Automation.Peers.AutomationPeer.UpdateSubtree()
at System.Windows.ContextLayoutManager.fireAutomationEvents()
at System.Windows.ContextLayoutManager.UpdateLayout()
at System.Windows.ContextLayoutManager.UpdateLayoutCallback(Object arg)
at System.Windows.Media.MediaContext.InvokeOnRenderCallback.DoWork()
at System.Windows.Media.MediaContext.FireInvokeOnRenderCallbacks()
at System.Windows.Media.MediaContext.RenderMessageHandlerCore(Object resizedCompositionTarget)
at System.Windows.Media.MediaContext.AnimatedRenderMessageHandler(Object resizedCompositionTarget)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Boolean isSingleParameter)
at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler)

This occurs just after a Page is loaded inside a Frame element, the page has a Grouped ListView where the Group's are templated with a button and the sub-items are only displayed as a tooltip. Repeated issues on a particular machine suggest it is related to the application running at the same time as the Webex client application
(http://www.webex.com.au/au/support/downloads-webex.html).

Details (expand)

English

.NET Framework 3.0

Windows Vista

English

1. Create a WPF application with a Window with a <Frame> inside it.
2. Add page and set the frame source to that page.
3. Add a ListView with the following Xaml.
<ListView
x:Name="OrderList"
SelectionMode="Extended"
ItemsSource="{Binding}"
Margin="0,0,5,5"
>
<ListView.GroupStyle>
<GroupStyle>
<GroupStyle.Panel>
<ItemsPanelTemplate>
<VirtualizingStackPanel x:Name="GroupStackPanel" IsVirtualizing="True" />
</ItemsPanelTemplate>
</GroupStyle.Panel>
<GroupStyle.ContainerStyle>
<Style TargetType="{x:Type GroupItem}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate>
<Button Margin="5,5,5,5" Click="GroupItem_Clicked" MinHeight="40">
<Button.ToolTip>
<Border MaxHeight="250" MaxWidth="400">
<ItemsPresenter />
</Border>
</Button.ToolTip>
<TextBlock FontWeight="DemiBold" Margin="5,5,5,5"><InlineUIContainer>
<TextBlock Text="{Binding Path=Name}" />
</InlineUIContainer><Run Text=" "/><Run Text=" ("/><Run Text=" "/><InlineUIContainer>
<TextBlock Text="{Binding Path=ItemCount}"/>
</InlineUIContainer><Run Text=" "/><Run Text=")" /></TextBlock>
</Button>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</GroupStyle.ContainerStyle>
</GroupStyle>
</ListView.GroupStyle>
</ListView>

4. Bind the Page to any data source.
5. Start the Webex client application
6. Run the WPF application

This should intermittently reproduce the issue (possibly a threading issue?).

Exception is thrown without a specific trigger by the application, and only on certain machine configurations.

Should either be able to catch the exception at a point where it can be handled cleanly, or not throw the exception. Additional details about the cause of the exception might also be useful.

0 attachments

Posted by DonovanH on 10/19/2011 at 5:19 PM

I can get this bug in my .NET 4.0 app 100% of the time when I navigate to a certain part of the app, as soon as any UI automation is enabled, e.g. using UISpy.

Posted by mirkoklemm on 9/15/2011 at 4:00 AM

I am Using .NET 4, but the issue persists for me.

Posted by Microsoft on 2/22/2008 at 10:55 AM

This issue has been fixed in the .Net 3.5 SP1 release

Posted by Microsoft on 12/11/2007 at 1:50 AM

Thanks for your feedback. We are escalating this issue to the appropriate group within the Visual Studio Product Team for triage and resolution. These specialized experts will follow-up with your issue.

Thank you,
Visual Studio Product Team

Posted by John Melville on 1/12/2008 at 11:32 PM

As mentioned in some of the confirmation messages, killing the TabTip process does, in fact, remedy this issue.