Value cannot be null exception

Docking/MDI for WPF Forum

Posted 7 months ago by Martin Votruba
Version: 17.2.0685
Platform: .NET 4.5
Environment: Windows 10 (64-bit)
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Hello,

I am using yours Docking component and after some change in the code I have done recently, a unhandled exception started to be raised when the applicaiton is run for some time. The exception is raised quite irregualry and thus I have not been able so far to observe the exception while debugging and all I have is the stack trace. I do not expect that you will be able to identify the exact cause of this exception, howerver I will highly appraciate any suggestions, what might be the cause. Even some explonation of what the DockingWindowContainerBaseAutomationPeer.GetChildrenCore() is doing might help to locate the bug.

An unhandled exception occurred: Value cannot be null.
Parameter name: element
at System.Windows.Automation.Peers.UIElementAutomationPeer.CreatePeerForElement(UIElement element)
at ActiproSoftware.Windows.Controls.Docking.Automation.Peers.DockingWindowContainerBaseAutomationPeer.GetChildrenCore()
at System.Windows.Automation.Peers.AutomationPeer.EnsureChildren()
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.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)

Thank you very much,

Martin

Comments (1)

Posted 7 months ago by Actipro Software Support - Cleveland, OH, USA
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Hello,

I'm sorry you're having trouble.  I see you are using our 2017.2 version.  Looking at our code notes, I believe this bug was fixed in the 2018.1 version.


Actipro Software Support

The latest build of this product (v2020.1.1) was released 15 days ago, which was after the last post in this thread.

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