WPF app crashes with KeyNotFoundException

[DenSmoke]

• .NET Core Version: 3.0.100
• Windows version: Microsoft Windows 10.0.18362
• Does the bug reproduce also in WPF for .NET Framework 4.8?: not sure, but 4.7.2 had this bug also

• Is this bug related specifically to tooling in Visual Studio (e.g. XAML Designer, Code editing, etc...)? No

  Problem description: WPF App crashes sometimes randomly with KeyNotFoundException

  Actual behavior:

  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.GetPeerFromWeakRefStorage(Object item)
  at System.Windows.Automation.Peers.ItemsControlAutomationPeer.AddProxyToWeakRefStorage(WeakReference wr, ItemAutomationPeer itemPeer)
  at System.Windows.Automation.Peers.ItemAutomationPeer.AddToParentProxyWeakRefCache()
  at MS.Internal.Automation.ElementProxy.StaticWrap(AutomationPeer peer, AutomationPeer referencePeer)
  at System.Windows.Automation.Peers.AutomationPeer.UpdateChildrenInternal(Int32 invalidateLimit)
  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.Automation.Peers.AutomationPeer.UpdateSubtree()
  at System.Windows.ContextLayoutManager.fireAutomationEvents()
  at System.Windows.ContextLayoutManager.UpdateLayout()
  at System.Windows.UIElement.UpdateLayout()
  at System.Windows.Controls.VirtualizingStackPanel.<>c__DisplayClass94_0.<InitializeViewport>b__0()
  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)

  Expected behavior: No error because this repo already has fix of .NET Framework 4.8: https://github.com/dotnet/wpf/blob/48990f1c1f1adb0b27213cb9dafcef6d812ef548/src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Automation/Peers/ItemsControlAutomationPeer.cs#L601-L607 Minimal repro: I can't even understand where and why this happens so don't know how it can be reproduced

[vatsan-madhavan]

@DenSmoke Do you have a crash-dump or a self-contained repro we can take a look at?

[DenSmoke]

@vatsan-madhavan Unfortunately I can't catch these crashes. I only get error reports from clients sometimes. I kept app running for 2 days with debugger but error didn't occur. I suspect app crashes with that exception on Windows 7 machines. I can't post code because of an NDA and can't create repro code because I don't know what causes it. But I can say that app uses no-codebehind design and almost every thing is written in XAML by a lot of Styles, DataTemplates, ControlTemplates.

If only I could get information what page or window gets this exception...

[mgnslndh]

I've had this crash on my app as well. This was on .NET Framework 4.7.2. I also compared the source code of .NET 4.7.2 and 4.8 and found the Contains check in .NET 4.8. I've upgraded my app so it is no longer a problem.

As far as why the key was missing I do not know. The app i'm writing is using touch (and tabtip.exe) other than that no UI automation is used.

https://stackoverflow.com/questions/58656290/how-can-itempeersstorage-throw-exception-when-getting-value-from-weakdictionary

[DenSmoke]

@vatsan-madhavan I remembered that app uses Microsoft.Maps.MapControl.WPF package which uses .NET Framework 4.0. I suppose this package uses .NET Framework installed on client's PC. So that's why error is more distributed among Win7 users because they don't have .NET Framework 4.8 by default. Is my assumption true?

[DenSmoke]

It seems my recommendation for clients to upgrade .NET Framework to 4.8 on their PCs resolved this problem