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I have for some time been using a CameraAxisPanel with no issues, however, something today has changed and I'm getting an exception. I have made some code changes but I'm not aware of doing anything related to the 3D view (obviously something has affected it however). I have the latest version of PowerToys (7.5.5960.1045) I have an entry in the my view:

<controls:CameraAxisPanel Name="AxisPanel" VerticalAlignment="Bottom" HorizontalAlignment="Left" Margin="30,5,5,30" Is3DAxesShown="False" IsAxisNameShown="True" />

The exception I get is very large and is shown at the end of this post. I have tried removing the entry above and the exception goes away, put it back again and it reappears. Any ideas?

System.NullReferenceException: Object reference not set to an instance of an object.
at .(FrameworkElement )
at Ab3d.Controls.CameraAxisPanel.(Boolean )
at Ab3d.Controls.CameraAxisPanel.(Object , DependencyPropertyChangedEventArgs )
at System.Windows.UIElement.RaiseDependencyPropertyChanged(EventPrivateKey key, DependencyPropertyChangedEventArgs args)
at System.Windows.UIElement.OnIsVisibleChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
at System.Windows.DependencyObject.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
at System.Windows.FrameworkElement.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
at System.Windows.DependencyObject.NotifyPropertyChange(DependencyPropertyChangedEventArgs args)
at System.Windows.UIElement.UpdateIsVisibleCache()
at System.Windows.UIElement.InvalidateForceInheritPropertyOnChildren(Visual v, DependencyProperty property)
at System.Windows.FrameworkElement.InvalidateForceInheritPropertyOnChildren(DependencyProperty property)
at System.Windows.UIElement.OnIsVisibleChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
at System.Windows.DependencyObject.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
at System.Windows.FrameworkElement.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
at System.Windows.DependencyObject.NotifyPropertyChange(DependencyPropertyChangedEventArgs args)
at System.Windows.UIElement.UpdateIsVisibleCache()
at System.Windows.UIElement.OnVisualParentChanged(DependencyObject oldParent)
at System.Windows.Media.Visual.FireOnVisualParentChanged(DependencyObject oldParent)
at System.Windows.Media.Visual.AddVisualChild(Visual child)
at System.Windows.FrameworkElement.set_TemplateChild(UIElement value)
at System.Windows.Controls.ContentPresenter.UseContentTemplate.BuildVisualTree(FrameworkElement container)
at System.Windows.StyleHelper.ApplyTemplateContent(UncommonField`1 dataField, DependencyObject container, FrameworkElementFactory templateRoot, Int32 lastChildIndex, HybridDictionary childIndexFromChildID, FrameworkTemplate frameworkTemplate)
at System.Windows.FrameworkTemplate.ApplyTemplateContent(UncommonField`1 templateDataField, FrameworkElement container)
at System.Windows.FrameworkElement.ApplyTemplate()
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at System.Windows.Controls.Border.MeasureOverride(Size constraint)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at System.Windows.Controls.Control.MeasureOverride(Size constraint)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at System.Windows.Controls.Grid.MeasureOverride(Size constraint)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at DevComponents.WpfDock.DockSite.MeasureArrange(Size arrangeBounds, Boolean isArrange)
at DevComponents.WpfDock.DockSite.MeasureOverride(Size constraint)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at System.Windows.Controls.Grid.MeasureCell(Int32 cell, Boolean forceInfinityV)
at System.Windows.Controls.Grid.MeasureCellsGroup(Int32 cellsHead, Size referenceSize, Boolean ignoreDesiredSizeU, Boolean forceInfinityV, Boolean& hasDesiredSizeUChanged)
at System.Windows.Controls.Grid.MeasureOverride(Size constraint)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at MS.Internal.Helper.MeasureElementWithSingleChild(UIElement element, Size constraint)
at System.Windows.Controls.ContentPresenter.MeasureOverride(Size constraint)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at System.Windows.Controls.Border.MeasureOverride(Size constraint)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at System.Windows.Controls.Control.MeasureOverride(Size constraint)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at System.Windows.Controls.Grid.MeasureCell(Int32 cell, Boolean forceInfinityV)
at System.Windows.Controls.Grid.MeasureCellsGroup(Int32 cellsHead, Size referenceSize, Boolean ignoreDesiredSizeU, Boolean forceInfinityV, Boolean& hasDesiredSizeUChanged)
at System.Windows.Controls.Grid.MeasureOverride(Size constraint)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at MS.Internal.Helper.MeasureElementWithSingleChild(UIElement element, Size constraint)
at System.Windows.Controls.ContentPresenter.MeasureOverride(Size constraint)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at System.Windows.Controls.DockPanel.MeasureOverride(Size constraint)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at System.Windows.Controls.Border.MeasureOverride(Size constraint)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at System.Windows.Controls.DockPanel.MeasureOverride(Size constraint)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at System.Windows.Controls.Border.MeasureOverride(Size constraint)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at System.Windows.Controls.Control.MeasureOverride(Size constraint)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at DevComponents.WpfDock.SplitPanel.MeasureArrange(Size finalSize, Boolean isArrange)
at DevComponents.WpfDock.SplitPanel.MeasureOverride(Size availableSize)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at DevComponents.WpfDock.DockSite.MeasureArrange(Size arrangeBounds, Boolean isArrange)
at DevComponents.WpfDock.DockSite.MeasureOverride(Size constraint)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at System.Windows.Controls.Grid.MeasureOverride(Size constraint)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at MS.Internal.Helper.MeasureElementWithSingleChild(UIElement element, Size constraint)
at System.Windows.Controls.ContentPresenter.MeasureOverride(Size constraint)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at System.Windows.Documents.AdornerDecorator.MeasureOverride(Size constraint)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at System.Windows.Controls.Border.MeasureOverride(Size constraint)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
at System.Windows.Window.MeasureOverrideHelper(Size constraint)
at System.Windows.Window.MeasureOverride(Size availableSize)
at System.Windows.FrameworkElement.MeasureCore(Size availableSize)
at System.Windows.UIElement.Measure(Size availableSize)
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)
at MS.Win32.UnsafeNativeMethods.CallWindowProc(IntPtr wndProc, IntPtr hWnd, Int32 msg, IntPtr wParam, IntPtr lParam)
at MS.Win32.HwndSubclass.DefWndProcWrapper(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
at MS.Win32.UnsafeNativeMethods.CallWindowProc(IntPtr wndProc, IntPtr hWnd, Int32 msg, IntPtr wParam, IntPtr lParam)
at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
I was not able to reproduce your problem.

But from the exception details I was able to improve the code so that it will not throw the null reference exception.

If you still have problems with this exception, please let me know and I will prepare a pre-release version for you.
(07-18-2016, 02:28 PM)abenedik Wrote: [ -> ]I was not able to reproduce your problem.

But from the exception details I was able to improve the code so that it will not throw the null reference exception.

If you still have problems with this exception, please let me know and I will prepare a pre-release version for you.

Hi, Thanks for looking into this. Yes a pre-release version would be appreciated

Tim
I did some additional testing and found a way to reproduce the problem.

The exception was thrown in CameraAxisPanel when the Is3DAxesShown property is set to false and the CameraAxisPanel was not yet loaded and its TargetCamera is already set.

One example of this is when the CameraAxisPanel is defined in code behind:

var cameraAxisPanel = new CameraAxisPanel();

cameraAxisPanel.TargetCamera = Camera1;
cameraAxisPanel.Is3DAxesShown = false; // This has thrown an exception
cameraAxisPanel.IsAxisNameShown = false;

This has been already fixed and will not happen any more in the future.

For the current version the workaround is to define the TargetCamera as the last property that is set in CameraAxisPanel. Another workaround is to set define the
CameraAxisPanel in XAML.