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System.NullReferenceException: in PropertyGrid

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indeni
4 posts

Hi Everyone,

We've had a chance to run in this:

System.NullReferenceException: Object reference not set to an instance of an object.
   at Mindscape.WpfPropertyGrid.TreeListView.#Ob(GridViewColumnCollection columns, DependencyProperty dp, Nullable`1 defaultIndex)
   at Mindscape.WpfPropertyGrid.TreeListView.#Qb(GridViewColumnCollection columns)
   at Mindscape.WpfPropertyGrid.TreeListView.#Vb(Object sender, MouseEventArgs e)
   at System.Windows.Input.MouseEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
   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.UIElement.RaiseTrustedEvent(RoutedEventArgs args)
   at System.Windows.UIElement.RaiseEvent(RoutedEventArgs args, Boolean trusted)
   at System.Windows.Input.InputManager.ProcessStagingArea()
   at System.Windows.Input.InputManager.ProcessInput(InputEventArgs input)
   at System.Windows.Input.MouseDevice.Synchronize()
   at System.Windows.Input.Mouse.Synchronize()
   at System.Windows.Controls.Primitives.Track.OnIsEnabledChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
   at System.Windows.PropertyChangedCallback.Invoke(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.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, Boolean coerceWithDeferredReference, Boolean coerceWithCurrentValue, OperationType operationType)
   at System.Windows.DependencyObject.CoerceValue(DependencyProperty dp)
   at System.Windows.UIElement.InvalidateForceInheritPropertyOnChildren(Visual v, DependencyProperty property)
   at System.Windows.UIElement.OnIsEnabledChanged(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.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, Boolean coerceWithDeferredReference, Boolean coerceWithCurrentValue, OperationType operationType)
   at System.Windows.DependencyObject.CoerceValue(DependencyProperty dp)
   at System.Windows.UIElement.InvalidateForceInheritPropertyOnChildren(Visual v, DependencyProperty property)
   at System.Windows.UIElement.OnIsEnabledChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
   at System.Windows.PropertyChangedCallback.Invoke(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.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, Boolean coerceWithDeferredReference, Boolean coerceWithCurrentValue, OperationType operationType)
   at System.Windows.DependencyObject.CoerceValue(DependencyProperty dp)
   at System.Windows.Controls.Primitives.ScrollBar.ViewChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
   at System.Windows.PropertyChangedCallback.Invoke(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.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, Boolean coerceWithDeferredReference, Boolean coerceWithCurrentValue, OperationType operationType)
   at System.Windows.DependencyObject.InvalidateProperty(DependencyProperty dp)
   at System.Windows.StyleHelper.InvalidateDependents(Style ownerStyle, FrameworkTemplate frameworkTemplate, DependencyObject container, DependencyProperty dp, FrugalStructList`1& dependents, Boolean invalidateOnlyContainer)
   at System.Windows.StyleHelper.OnTriggerSourcePropertyInvalidated(Style ownerStyle, FrameworkTemplate frameworkTemplate, DependencyObject container, DependencyProperty dp, DependencyPropertyChangedEventArgs changedArgs, Boolean invalidateOnlyContainer, FrugalStructList`1& triggerSourceRecordFromChildIndex, FrugalMap& propertyTriggersWithActions, Int32 sourceChildIndex)
   at System.Windows.FrameworkElement.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
   at System.Windows.DependencyObject.NotifyPropertyChange(DependencyPropertyChangedEventArgs args)
   at System.Windows.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, Boolean coerceWithDeferredReference, Boolean coerceWithCurrentValue, OperationType operationType)
   at System.Windows.DependencyObject.SetValueCommon(DependencyProperty dp, Object value, PropertyMetadata metadata, Boolean coerceWithDeferredReference, Boolean coerceWithCurrentValue, OperationType operationType, Boolean isInternal)
   at System.Windows.DependencyObject.SetValue(DependencyPropertyKey key, Object value)
   at System.Windows.Controls.ScrollViewer.OnLayoutUpdated(Object sender, EventArgs e)
   at System.Windows.ContextLayoutManager.fireLayoutUpdateEvent()
   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 MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)

Any idea what was null there and how do we avoid it?

Thanks,

yonadav

Posted on Mar 29 2010

ivan
5,431 posts

The only thing that I can see that might be null in that method is if one of the columns of the TreeListView is null. This should not be possible using the normal PropertyGrid -- are you using the TreeListView directly, either as a standalone control or in a PropertyGrid ControlTemplate? When in the application does it occur? Can you provide us with code and instructions to reproduce the error?

Posted on Mar 29 2010

indeni
4 posts

Hi Ivan,

Actually this happened only once during testing, but has crashed the application completely. We have not been able to reproduce it yet.

We're using the property grid as-is, not any of its controls directly, so it's not clear to us how this happened. Is it possible that during the control's removal something was removed but this method was still called? Some kind of race condition perhaps?

Thanks,

yonadav

Posted on Mar 30 2010

mcdrewski
49 posts

As a tip, i've seen similar behaviour before where an exception has been thrown in my own code. we have manually caught that exception to display a "nice" error message, but displaying that "nice" dialog to the user causes the windows message pump to again be handled. This in turn invokes update and draw behaviours on existing controls which then fail spectacularly (because the init() code throwing the original exception never completed).

It often shows up in our crash reporting framework as an obscure crash in some third party control when in fact the "cause" was another exception entirely.

Not trying to absolve the control of blame - just saying it's something that i consciously look for now with obscure deep-control crashes.

Posted on Mar 30 2010

indeni 4 posts	Thanks for the tip! Posted on Apr 07 2010

System.NullReferenceException: in PropertyGrid

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