NullReferenceException at OnMouseEnter in LayoutAnchorableTabItem

[Chocko]

Hello,

when using the Avalon Dock v3.4 (i.e. Git Commit c0d3a0a), there are sporadic NullReferenceExceptions in the OnMouseEnter method in the LayoutAnchorableTabItem (line 197). I guess its the "_draggingItem" which is null.

Line 197:
containerPane.MoveChild( childrenList.IndexOf( _draggingItem.Model ), childrenList.IndexOf( model ) );

Details:
System.NullReferenceException
HResult=0x80004003
Message=Object reference not set to an instance of an object.
Source=Xceed.Wpf.AvalonDock
StackTrace:
at Xceed.Wpf.AvalonDock.Controls.LayoutAnchorableTabItem.OnMouseEnter(MouseEventArgs e) in (...)\wpftoolkit\ExtendedWPFToolkitSolution\Src\Xceed.Wpf.AvalonDock\Controls\LayoutAnchorableTabItem.cs:line 197

[Chocko]

Btw, in Commit 24ecc09 (v3.4) there was the check at the beginning of the method (_draggingItem != null) removed...

[isbeorn]

Hi there,

my application experiences the same issue after updating to avalondock 3.4.

Object reference not set to an instance of an object. at Xceed.Wpf.AvalonDock.Controls.LayoutAnchorableTabItem.OnMouseEnter(MouseEventArgs e)
at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
at System.Windows.ReverseInheritProperty.FirePropertyChangeInAncestry(DependencyObject element, Boolean oldValue, DeferredElementTreeState treeState, Action2 originChangedAction) at System.Windows.ReverseInheritProperty.FirePropertyChangeInAncestry(DependencyObject element, Boolean oldValue, DeferredElementTreeState treeState, Action2 originChangedAction)
at System.Windows.ReverseInheritProperty.FirePropertyChangeInAncestry(DependencyObject element, Boolean oldValue, DeferredElementTreeState treeState, Action2 originChangedAction) at System.Windows.ReverseInheritProperty.FirePropertyChangeInAncestry(DependencyObject element, Boolean oldValue, DeferredElementTreeState treeState, Action2 originChangedAction)
at System.Windows.ReverseInheritProperty.FirePropertyChangeInAncestry(DependencyObject element, Boolean oldValue, DeferredElementTreeState treeState, Action2 originChangedAction) at System.Windows.ReverseInheritProperty.FirePropertyChangeInAncestry(DependencyObject element, Boolean oldValue, DeferredElementTreeState treeState, Action2 originChangedAction)
at System.Windows.ReverseInheritProperty.FirePropertyChangeInAncestry(DependencyObject element, Boolean oldValue, DeferredElementTreeState treeState, Action2 originChangedAction) at System.Windows.ReverseInheritProperty.FirePropertyChangeInAncestry(DependencyObject element, Boolean oldValue, DeferredElementTreeState treeState, Action2 originChangedAction)
at System.Windows.ReverseInheritProperty.FirePropertyChangeInAncestry(DependencyObject element, Boolean oldValue, DeferredElementTreeState treeState, Action2 originChangedAction) at System.Windows.ReverseInheritProperty.OnOriginValueChanged(DependencyObject oldOrigin, DependencyObject newOrigin, IList1 otherOrigins, DeferredElementTreeState& oldTreeState, Action`2 originChangedAction)
at System.Windows.Input.MouseDevice.ChangeMouseOver(IInputElement mouseOver, Int32 timestamp)
at System.Windows.Input.MouseDevice.PreNotifyInput(Object sender, NotifyInputEventArgs e)
at System.Windows.Input.InputManager.ProcessStagingArea()
at System.Windows.Input.InputManager.ProcessInput(InputEventArgs input)
at System.Windows.Input.InputProviderSite.ReportInput(InputReport inputReport)
at System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel)
at System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at System.Windows.Interop.HwndSource.InputFilterMessage(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)

[Chocko]

Hi isbeorn,

thanks for your answer. Just in case you need a workaround: I have downloaded the repository and added the null-check at line 184 like this:

if( _draggingItem != null && 
    _draggingItem != this &&
    e.LeftButton == MouseButtonState.Pressed )

I guess this solves the issue...

Here is a patch file:
issue#1354_workaround_patch.diff.txt

[XceedBoucherS]

Hi,
This is already fixed in v3.5 and up with the check " _draggingItem != null".
Thank you.

[PavelG2010]

This is already fixed in v3.5 and up with the check " _draggingItem != null".

I downloaded the latest version 3.7 and watch the error "NullReferenceException in LayoutAnchorableTabItem"

[XceedBoucherS]

Hi,
The v3.7 Plus version (free for 45 days) is only available on Xceed web site : https://xceed.com/xceed-toolkit-plus-for-wpf/
If this is the version you tested with the issue, can you explain in details your steps to reproduce the issue and give us the sample code you used.
Thank you.

[snooka2197]

This is already fixed in v3.5 and up with the check " _draggingItem != null".

Any ETA when v3.5 (non Plus version) is available?

[JobaDiniz]

This is already fixed in v3.5 and up with the check " _draggingItem != null".

Any ETA when v3.5 (non Plus version) is available?

I don't understand wpftoolkit patches releases... this fix should be out there, it's been 6 months :(

[dgosbell]

So is a new release due our soon? Or do I need to either rollback to 3.3 or fork the repo and fix this myself?

[JobaDiniz]

or fork the repo and fix this myself?

I did just that... the only thing that is needed is if (_draggingItem != null ...) and bug goes away