The exception occurred when we clicked the RadComboBox to update the items.

EXCEPTION :System.ArgumentNullException: Value cannot be null.
Parameter name: key
   at System.ThrowHelper.ThrowArgumentNullException(ExceptionArgument argument)
   at System.Collections.Generic.Dictionary`2.FindEntry(TKey key)
   at Telerik.Windows.Automation.Peers.RadComboBoxAutomationPeer.CreateItemAutomationPeer(Object item)
   at System.Windows.Automation.Peers.ItemsControlAutomationPeer.GetChildrenCore()
   at Telerik.Windows.Automation.Peers.RadComboBoxAutomationPeer.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.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.FireInvokeOnRenderCallbacks()
   at System.Windows.Media.MediaContext.RenderMessageHandlerCore(Object resizedCompositionTarget)
   at System.Windows.Media.MediaContext.RenderMessageHandler(Object resizedCompositionTarget)
   at System.Windows.Interop.HwndTarget.OnResize()
   at System.Windows.Interop.HwndTarget.HandleMessage(WindowMessage msg, IntPtr wparam, IntPtr lparam)
   at System.Windows.Interop.HwndSource.HwndTargetFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
   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)
   at System.Windows.Threading.Dispatcher.LegacyInvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
   at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)

Hello Yoan,

We are running 2017.1.222.45. I will see if we can reproduce the bug with this and the latest one.

Regards,
Thomas

Hi Yoan,

I got the same exception with Thomas. My version is 2017.3.1010.40. Can you check this one for me, please?

System.Transactions Critical: 0 : <TraceRecord xmlns="http://schemas.microsoft.com/2004/10/E2ETraceEvent/TraceRecord" Severity="Critical"><TraceIdentifier>http://msdn.microsoft.com/TraceCodes/System/ActivityTracing/2004/07/Reliability/Exception/Unhandled</TraceIdentifier><Description>Unhandled exception</Description><AppDomain>HistoTrac.exe</AppDomain><Exception><ExceptionType>System.ArgumentNullException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</ExceptionType><Message>Value cannot be null.
Parameter name: key</Message><StackTrace>   at System.Collections.Generic.Dictionary`2.FindEntry(TKey key)
   at Telerik.Windows.Automation.Peers.RadListBoxAutomationPeer.CreateItemAutomationPeer(Object item)
   at System.Windows.Automation.Peers.ItemsControlAutomationPeer.GetChildrenCore()
   at System.Windows.Automation.Peers.AutomationPeer.EnsureChildren()
   at System.Windows.Automation.Peers.AutomationPeer.GetChildren()
   at System.Windows.Automation.Peers.AutomationPeer.isDescendantOf(AutomationPeer parent)
   at System.Windows.Automation.Peers.AutomationPeer.isDescendantOf(AutomationPeer parent)
   at System.Windows.Automation.Peers.AutomationPeer.isDescendantOf(AutomationPeer parent)
   at System.Windows.Automation.Peers.AutomationPeer.ValidateConnected(AutomationPeer connectedPeer)
   at System.Windows.Automation.Peers.AutomationPeer.AutomationPeerFromInputElement(IInputElement focusedElement)
   at System.Windows.Automation.Peers.AutomationPeer.RaiseFocusChangedEventHelper(IInputElement newFocus)
   at System.Windows.Input.KeyboardDevice.ChangeFocus(DependencyObject focus, Int32 timestamp)
   at System.Windows.Input.KeyboardDevice.TryChangeFocus(DependencyObject newFocus, IKeyboardInputProvider keyboardInputProvider, Boolean askOld, Boolean askNew, Boolean forceToNullIfFailed)
   at System.Windows.Input.KeyboardDevice.Focus(DependencyObject focus, Boolean askOld, Boolean askNew, Boolean forceToNullIfFailed)
   at System.Windows.Input.KeyboardDevice.Focus(IInputElement element)
   at System.Windows.Interop.HwndKeyboardInputProvider.OnSetFocus(IntPtr hwnd)
   at System.Windows.Interop.HwndKeyboardInputProvider.FilterMessage(IntPtr hwnd, WindowMessage message, IntPtr wParam, IntPtr lParam, Boolean&amp;amp; handled)
   at System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean&amp;amp; handled)
   at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean&amp;amp; handled)
   at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
   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)
   at System.Windows.Threading.Dispatcher.LegacyInvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
   at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)</StackTrace><ExceptionString>System.ArgumentNullException: Value cannot be null.
Parameter name: key
   at System.Collections.Generic.Dictionary`2.FindEntry(TKey key)
   at Telerik.Windows.Automation.Peers.RadListBoxAutomationPeer.CreateItemAutomationPeer(Object item)
   at System.Windows.Automation.Peers.ItemsControlAutomationPeer.GetChildrenCore()
   at System.Windows.Automation.Peers.AutomationPeer.EnsureChildren()
   at System.Windows.Automation.Peers.AutomationPeer.GetChildren()
   at System.Windows.Automation.Peers.AutomationPeer.isDescendantOf(AutomationPeer parent)
   at System.Windows.Automation.Peers.AutomationPeer.isDescendantOf(AutomationPeer parent)
   at System.Windows.Automation.Peers.AutomationPeer.isDescendantOf(AutomationPeer parent)
   at System.Windows.Automation.Peers.AutomationPeer.ValidateConnected(AutomationPeer connectedPeer)
   at System.Windows.Automation.Peers.AutomationPeer.AutomationPeerFromInputElement(IInputElement focusedElement)
   at System.Windows.Automation.Peers.AutomationPeer.RaiseFocusChangedEventHelper(IInputElement newFocus)
   at System.Windows.Input.KeyboardDevice.ChangeFocus(DependencyObject focus, Int32 timestamp)
   at System.Windows.Input.KeyboardDevice.TryChangeFocus(DependencyObject newFocus, IKeyboardInputProvider keyboardInputProvider, Boolean askOld, Boolean askNew, Boolean forceToNullIfFailed)
   at System.Windows.Input.KeyboardDevice.Focus(DependencyObject focus, Boolean askOld, Boolean askNew, Boolean forceToNullIfFailed)
   at System.Windows.Input.KeyboardDevice.Focus(IInputElement element)
   at System.Windows.Interop.HwndKeyboardInputProvider.OnSetFocus(IntPtr hwnd)
   at System.Windows.Interop.HwndKeyboardInputProvider.FilterMessage(IntPtr hwnd, WindowMessage message, IntPtr wParam, IntPtr lParam, Boolean&amp;amp; handled)
   at System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean&amp;amp; handled)
   at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean&amp;amp; handled)
   at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
   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)
   at System.Windows.Threading.Dispatcher.LegacyInvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
   at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)</ExceptionString><DataItems><Data></Data></DataItems></Exception></TraceRecord>
An unhandled exception of type 'System.ArgumentNullException' occurred in mscorlib.dll
Value cannot be null.

Hi Thien,

As discussed in a ticket thread, disabling the automation pears remove the exception. Still, I would recommend using the latest version of our controls, where this exception is not reproducible.

Regards,
Dinko
Progress Telerik