调用删除操作的代码通常是有效的,但这是我第一次收到NullReferenceException异常。我正在尝试弄清楚是否可能出现了问题,并且是否可以避免此异常以使软件更加健壮。
相对较大数量的System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren调用似乎有点奇怪。
任何帮助都将不胜感激。
操作系统:6.1.7600.0 .NET版本:4.0.30319.225
堆栈:
at System.Windows.DependencyPropertyChangedEventArgs.get_OldValue()
at System.Windows.Controls.Control.OnTemplateChanged(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.InvalidateContainerDependents(DependencyObject container, FrugalStructList`1_ exclusionContainerDependents, FrugalStructList`1_ oldContainerDependents, FrugalStructList`1_ newContainerDependents)
at System.Windows.StyleHelper.DoStyleInvalidations(FrameworkElement fe, FrameworkContentElement fce, Style oldStyle, Style newStyle)
at System.Windows.StyleHelper.UpdateStyleCache(FrameworkElement fe, FrameworkContentElement fce, Style oldStyle, Style newStyle, Style_ styleCache)
at System.Windows.FrameworkElement.OnStyleChanged(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.FrameworkElement.UpdateStyleProperty()
at System.Windows.FrameworkElement.InvalidateTreeDependentProperties(TreeChangeInfo parentTreeState, Boolean isSelfInheritanceParent)
at System.Windows.FrameworkElement.OnAncestorChangedInternal(TreeChangeInfo parentTreeState)
at System.Windows.TreeWalkHelper.OnAncestorChanged(DependencyObject d, TreeChangeInfo info)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkLogicalChildren(FrameworkElement feParent, FrameworkContentElement fceParent, IEnumerator logicalChildren)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1._VisitNode(DependencyObject d)
at MS.Internal.PrePostDescendentsWalker`1._VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.VisitNode(FrameworkElement fe)
at System.Windows.DescendentsWalker`1.VisitNode(DependencyObject d)
at System.Windows.DescendentsWalker`1.WalkFrameworkElementLogicalThenVisualChildren(FrameworkElement feParent, Boolean hasLogicalChildren)
at System.Windows.DescendentsWalker`1.IterateChildren(DependencyObject d)
at System.Windows.DescendentsWalker`1.StartWalk(DependencyObject startNode, Boolean skipStartNode)
at MS.Internal.PrePostDescendentsWalker`1.StartWalk(DependencyObject startNode, Boolean skipStartNode)
at System.Windows.TreeWalkHelper.InvalidateOnTreeChange(FrameworkElement fe, FrameworkContentElement fce, DependencyObject parent, Boolean isAddOperation)
at System.Windows.FrameworkElement.OnVisualParentChanged(DependencyObject oldParent)
at System.Windows.Controls.ListBoxItem.OnVisualParentChanged(DependencyObject oldParent)
at System.Windows.Media.Visual.FireOnVisualParentChanged(DependencyObject oldParent)
at System.Windows.Media.Visual.RemoveVisualChild(Visual child)
at System.Windows.Media.VisualCollection.DisconnectChild(Int32 index)
at System.Windows.Media.VisualCollection.RemoveRange(Int32 index, Int32 count)
at System.Windows.Controls.UIElementCollection.RemoveRangeInternal(Int32 index, Int32 count)
at System.Windows.Controls.VirtualizingStackPanel.RemoveChildRange(GeneratorPosition position, Int32 itemCount, Int32 itemUICount)
at System.Windows.Controls.VirtualizingStackPanel.OnItemsRemove(ItemsChangedEventArgs args)
at System.Windows.Controls.VirtualizingStackPanel.OnItemsChanged(Object sender, ItemsChangedEventArgs args)
at System.Windows.Controls.VirtualizingPanel.OnItemsChangedInternal(Object sender, ItemsChangedEventArgs args)
at System.Windows.Controls.Panel.OnItemsChanged(Object sender, ItemsChangedEventArgs args)
at System.Windows.Controls.ItemContainerGenerator.OnItemRemoved(Object item, Int32 itemIndex)
at System.Windows.Controls.ItemContainerGenerator.OnCollectionChanged(Object sender, NotifyCollectionChangedEventArgs args)
at System.Windows.Controls.ItemContainerGenerator.System.Windows.IWeakEventListener.ReceiveWeakEvent(Type managerType, Object sender, EventArgs e)
at System.Windows.WeakEventManager.DeliverEventToList(Object sender, EventArgs args, ListenerList list)
at System.Windows.WeakEventManager.DeliverEvent(Object sender, EventArgs args)
at System.Collections.Specialized.CollectionChangedEventManager.OnCollectionChanged(Object sender, NotifyCollectionChangedEventArgs args)
at System.Collections.Specialized.NotifyCollectionChangedEventHandler.Invoke(Object sender, NotifyCollectionChangedEventArgs e)
at System.Windows.Data.CollectionView.OnCollectionChanged(NotifyCollectionChangedEventArgs args)
at System.Windows.Controls.ItemCollection.System.Windows.IWeakEventListener.ReceiveWeakEvent(Type managerType, Object sender, EventArgs e)
at System.Windows.WeakEventManager.DeliverEventToList(Object sender, EventArgs args, ListenerList list)
at System.Windows.WeakEventManager.DeliverEvent(Object sender, EventArgs args)
at System.Collections.Specialized.CollectionChangedEventManager.OnCollectionChanged(Object sender, NotifyCollectionChangedEventArgs args)
at System.Windows.Data.CollectionView.OnCollectionChanged(NotifyCollectionChangedEventArgs args)
at System.Windows.Data.ListCollectionView.ProcessCollectionChangedWithAdjustedIndex(NotifyCollectionChangedEventArgs args, Int32 adjustedOldIndex, Int32 adjustedNewIndex)
at System.Windows.Data.ListCollectionView.ProcessCollectionChanged(NotifyCollectionChangedEventArgs args)
at System.Windows.Data.CollectionView.OnCollectionChanged(Object sender, NotifyCollectionChangedEventArgs args)
at System.Collections.ObjectModel.ObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e)
at System.Collections.ObjectModel.ObservableCollection`1.RemoveItem(Int32 index)
at System.Collections.ObjectModel.Collection`1.Remove(T item)