System.Windows.ContextLayoutManager.UpdateLayout() throws KeyNotFoundException

Description

I get this exception quite often in my .NET 4.8 WPF app. The error is sent from clients automatically and I do not know how to reproduce it, or from what part of the code it originates.

I found a similar issue saying it had been fixed in 4.8: [https://github.com/dotnet/wpf/issues/2152]

System.Collections.Generic.KeyNotFoundException: The given key was not present in the dictionary.
   at MS.Internal.WeakDictionary`2.get_Item(TKey key)
   at System.Windows.Automation.Peers.ItemPeersStorage`1.get_Item(Object item)
   at System.Windows.Automation.Peers.ItemsControlAutomationPeer.GetChildrenCore()
   at System.Windows.Automation.Peers.ListViewAutomationPeer.GetChildrenCore()
   at System.Windows.Automation.Peers.AutomationPeer.EnsureChildren()
   at System.Windows.Automation.Peers.AutomationPeer.UpdateChildrenInternal(Int32 invalidateLimit)
   at System.Windows.Automation.Peers.ItemsControlAutomationPeer.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.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.RenderMessageHandler(Object resizedCompositionTarget)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)

Reproduction Steps

Don’t know.

Expected behavior

No exception

Actual behavior

Program crashes?

Regression?

No response

Known Workarounds

No response

Impact

No response

Configuration

.NET 4.8 Windows 10 x64

Other information

No response

[tripleacoder]

We also have this problem. Our WPF application crashes at random. We tried updating .NET Framework from 4.7.2 to 4.8 but it didn’t help. Our application also extensively uses DispatchTimer, Dispatcher.Invoke() and we also rely heavily on async/await for I/O operations.

Unfortunately, I can’t provide reliable reproduction at this time. Our application crashes roughly once per day which makes it impossible to ship, yet very hard to diagnose.

Any help or suggestions would be much appreciated.

@tripleacoder, did you have any success with this issue?

I never solved it. Instead I have made a workaround that simply ignores the exception in my global exception handling code:

private void HandleUnhandledExceptions(DispatcherUnhandledExceptionEventArgs e)
        {
            e.Handled = false; // true; // program lives, false = windows will close it

            Exception exception = e.Exception;

            if (exception is System.Collections.Generic.KeyNotFoundException)
            {
                if (exception.StackTrace.Contains("System.Windows.Automation.Peers.ItemPeersStorage"))
                {
                    // This exception is described here:
                    // https://dev.azure.com/REDACTED/_workitems/edit/4094
                    // Cause: unknown.
                    // It does not affect the user in any way, so we can just ignore it. Don't send any emails to the dev either.
                    e.Handled = true;
                }
                else
                {
                    this.vm.HandleUserException(exception, false);
                }
            }
            else
            {
                this.vm.HandleUserException(exception, true);
            }
        }

[miloush]

I can imagine this happening when the item is removed between the check and usage, classic race condition:

https://github.com/dotnet/wpf/blob/b148c5c887e11f5bc1e40c01fa319ab24852e4b1/src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Automation/Peers/ItemsControlAutomationPeer.cs#L603-L606

That’s why TryGet methods were introduced. However, looking at WeakDictionary, this is not doing much better either:

https://github.com/dotnet/wpf/blob/b148c5c887e11f5bc1e40c01fa319ab24852e4b1/src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/WeakDictionary.cs#L225-L229

~Fix seems straightforward, but will need to touch WeakDictionary~