Rare crash cell automation peer when changing selected row in datagrid

[cbra-caa]

Description

We experience a rare crash when the selected item is changed in the datagrid that result in a NPE:

System.ArgumentNullException: Value cannot be null. Parameter name: item at System.Windows.Automation.Peers.DataGridCellItemAutomationPeer..ctor(Object item, DataGridColumn dataGridColumn) at System.Windows.Automation.Peers.DataGridItemAutomationPeer.GetOrCreateCellItemPeer(DataGridColumn column, Boolean addParentInfo) at System.Windows.Automation.Peers.DataGridAutomationPeer.GetCellItemPeer(DataGridCellInfo cellInfo) at System.Windows.Automation.Peers.DataGridAutomationPeer.RaiseAutomationCellSelectedEvent(SelectedCellsChangedEventArgs e) at System.Windows.Controls.DataGrid.OnSelectedCellsChanged(SelectedCellsChangedEventArgs e) at System.Windows.Controls.DataGrid.NotifySelectedCellsChanged() at System.Windows.Controls.DataGrid.ChangingSelectedCellsHelper.Dispose() at System.Windows.Controls.DataGrid.OnSelectionChanged(SelectionChangedEventArgs e) at System.Windows.Controls.Primitives.Selector.SelectionChanger.End() at System.Windows.Controls.Primitives.Selector.OnSelectedItemsCollectionChanged(Object sender, NotifyCollectionChangedEventArgs e) at System.Collections.ObjectModel.ObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e) at System.Collections.ObjectModel.ObservableCollection`1.InsertItem(Int32 index, T item) at System.Windows.Controls.SelectedItemCollection.InsertItem(Int32 index, Object item) at System.Collections.ObjectModel.Collection`1.System.Collections.IList.Add(Object value)

or

System.ArgumentNullException: En værdi må ikke være null. Parameternavn: item ved System.Windows.Automation.Peers.DataGridCellItemAutomationPeer..ctor(Object item, DataGridColumn dataGridColumn) ved System.Windows.Automation.Peers.DataGridItemAutomationPeer.GetOrCreateCellItemPeer(DataGridColumn column, Boolean addParentInfo) ved System.Windows.Automation.Peers.DataGridAutomationPeer.GetCellItemPeer(DataGridCellInfo cellInfo) ved System.Windows.Automation.Peers.DataGridAutomationPeer.RaiseAutomationCellSelectedEvent(SelectedCellsChangedEventArgs e) ved System.Windows.Controls.DataGrid.OnSelectedCellsChanged(SelectedCellsChangedEventArgs e) ved System.Windows.Controls.DataGrid.NotifySelectedCellsChanged() ved System.Windows.Controls.DataGrid.ChangingSelectedCellsHelper.Dispose() ved System.Windows.Controls.DataGrid.AdjustPendingInfos() ved System.Windows.Controls.DataGrid.AdjustItemInfosAfterGeneratorChangeOverride() ved System.Windows.Controls.Primitives.Selector.AdjustNewContainers() ved System.Windows.Controls.Primitives.Selector.OnGeneratorStatusChanged(Object sender, EventArgs e) ved System.Windows.Controls.ItemContainerGenerator.SetStatus(GeneratorStatus value) ved System.Windows.Controls.ItemContainerGenerator.BatchGenerator.System.IDisposable.Dispose() ved System.Windows.Controls.VirtualizingStackPanel.MeasureOverrideImpl(Size constraint, Nullable`1& lastPageSafeOffset, List`1& previouslyMeasuredOffsets, Nullable`1& lastPagePixelSize, Boolean remeasure) ved System.Windows.Controls.VirtualizingStackPanel.MeasureOverride(Size constraint) ved System.Windows.Controls.Primitives.DataGridRowsPresenter.MeasureOverride(Size constraint) ved System.Windows.FrameworkElement.MeasureCore(Size availableSize) ved System.Windows.UIElement.Measure(Size availableSize) ved System.Windows.ContextLayoutManager.UpdateLayout() ved System.Windows.ContextLayoutManager.UpdateLayoutCallback(Object arg) ved System.Windows.Media.MediaContext.FireInvokeOnRenderCallbacks() ved System.Windows.Media.MediaContext.RenderMessageHandlerCore(Object resizedCompositionTarget) ved System.Windows.Media.MediaContext.RenderMessageHandler(Object resizedCompositionTarget) ved System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) ved System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)

The stacktrace might differ a bit from case-to-case but it always reaches OnSelectedCellsChanged(...) from which the road to the cell peer ctor is the same.

Reproduction Steps

None known. We have seen it across 12 different users over a period of 3 months.

Expected behavior

The client does not crash on a peer being created.

Actual behavior

The client crashes unexpectedly.

Regression?

Not that we know of.

Known Workarounds

We have just added a try-catch as an override on base.OnSelectedCellsChanged(...) but due to how rare the issue is, we have no way of knowing whether this solves the issues, or if it just leads to a bad state from which the client might/might not be able to continue.

Impact

Problem seems to be able to hit all users, regardless of them working on laptops, desktops, screen sizes, remote state and hardware acceleration.

Configuration

• .net framework 4.8
• Windows - newest version (over a 3-month period)
• x86
• Not confirmed

Other information

The datagrid we utilize is running with both sorting and filtering, so we have a lot of moving parts. In addition virtualization is also enabled, both horizontally and vertically since there might be a lot of columns, for a bunch of data.

[harshit7962]

@cbra-caa can you please confirm if you can also repro this issue in .NET core.

[cbra-caa]

We have no known way of reproducing this, neither in Framework nor Core.

The scope of the problem is not wide - we have several thousand users running the app, but only 12 of those has experienced the problem over a 3 month period. The stacktraces are not aligned expect for where they end. Of those 12 we get 9 distinct paths that all lead to OnSelectedCellsChanged - most of them pure WPF traces.

It happens on the user selecting items, navigating to/from the datagrid.
It happens on load, unload, and on items changed.

Going through the open and closed issues reveals no other references to DataGridCellItemAutomationPeer so I wouldn't expect it to be fixed, unless there has been a rewrite on the path:

System.Windows.Automation.Peers.DataGridCellItemAutomationPeer..ctor(Object item, DataGridColumn dataGridColumn) at System.Windows.Automation.Peers.DataGridItemAutomationPeer.GetOrCreateCellItemPeer(DataGridColumn column, Boolean addParentInfo) at System.Windows.Automation.Peers.DataGridAutomationPeer.GetCellItemPeer(DataGridCellInfo cellInfo) at System.Windows.Automation.Peers.DataGridAutomationPeer.RaiseAutomationCellSelectedEvent(SelectedCellsChangedEventArgs e) at System.Windows.Controls.DataGrid.OnSelectedCellsChanged(SelectedCellsChangedEventArgs e)