NullReferenceException on Dispose

I saw several threads for IOS and Xamarin Forms with the same issue.  Using version 16.3.0.29.

System.NullReferenceException: Object reference not set to an instance of an object.
   at Syncfusion.UI.Xaml.Gauges.CircularScale.CreateTicks()
   at Syncfusion.UI.Xaml.Gauges.CircularScale.OnRangeValueChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
   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, Boolean preserveCurrentValue)
   at System.Windows.Data.BindingExpressionBase.Invalidate(Boolean isASubPropertyChange)
   at System.Windows.Data.BindingExpression.TransferValue(Object newValue, Boolean isASubPropertyChange)
   at System.Windows.Data.BindingExpression.Activate(Object item)
   at System.Windows.Data.BindingExpression.OnDataContextChanged(DependencyObject contextElement)
   at System.Windows.Data.BindingExpression.HandlePropertyInvalidation(DependencyObject d, DependencyPropertyChangedEventArgs args)
   at System.Windows.Data.BindingExpressionBase.OnPropertyInvalidation(DependencyObject d, DependencyPropertyChangedEventArgs args)
   at System.Windows.Data.BindingExpression.OnPropertyInvalidation(DependencyObject d, DependencyPropertyChangedEventArgs args)
   at System.Windows.DependentList.InvalidateDependents(DependencyObject source, DependencyPropertyChangedEventArgs sourceArgs)
   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.TreeWalkHelper.InvalidateTreeDependentProperty(TreeChangeInfo info, DependencyObject d, FrameworkObject& fo, DependencyProperty dp, FrameworkPropertyMetadata fMetadata, Style selfStyle, Style selfThemeStyle, ChildRecord& childRecord, Boolean isChildRecordValid, Boolean hasStyleChanged, Boolean isSelfInheritanceParent, Boolean wasSelfInheritanceParent)
   at System.Windows.TreeWalkHelper.InvalidateTreeDependentProperties(TreeChangeInfo info, FrameworkElement fe, FrameworkContentElement fce, Style selfStyle, Style selfThemeStyle, ChildRecord& childRecord, Boolean isChildRecordValid, Boolean hasStyleChanged, Boolean isSelfInheritanceParent, Boolean wasSelfInheritanceParent)
   at System.Windows.FrameworkElement.InvalidateTreeDependentProperties(TreeChangeInfo parentTreeState, Boolean isSelfInheritanceParent, Boolean wasSelfInheritanceParent)
   at System.Windows.FrameworkElement.OnAncestorChangedInternal(TreeChangeInfo parentTreeState)
   at System.Windows.TreeWalkHelper.OnAncestorChanged(DependencyObject d, TreeChangeInfo info, Boolean visitedViaVisualTree)
   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.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.Clear()
   at System.Windows.Controls.UIElementCollection.ClearInternal()
   at System.Windows.Controls.Panel.ClearChildren()
   at System.Windows.Controls.Panel.OnItemsChangedInternal(Object sender, ItemsChangedEventArgs args)
   at System.Windows.Controls.Panel.OnItemsChanged(Object sender, ItemsChangedEventArgs args)
   at System.Windows.Controls.ItemContainerGenerator.OnRefresh()
   at System.Windows.Controls.ItemContainerGenerator.OnCollectionChanged(Object sender, NotifyCollectionChangedEventArgs args)
   at System.Windows.WeakEventManager.ListenerList`1.DeliverEvent(Object sender, EventArgs e, Type managerType)
   at System.Windows.WeakEventManager.DeliverEvent(Object sender, EventArgs args)
   at System.Collections.Specialized.NotifyCollectionChangedEventHandler.Invoke(Object sender, NotifyCollectionChangedEventArgs e)
   at System.Windows.Data.CollectionView.OnCollectionChanged(NotifyCollectionChangedEventArgs args)
   at System.Windows.WeakEventManager.ListenerList`1.DeliverEvent(Object sender, EventArgs e, Type managerType)
   at System.Windows.WeakEventManager.DeliverEvent(Object sender, EventArgs args)
   at System.Windows.Data.CollectionView.OnCollectionChanged(NotifyCollectionChangedEventArgs args)
   at System.Windows.Data.ListCollectionView.RefreshOverride()
   at System.Windows.Data.CollectionView.RefreshInternal()
   at System.Collections.Specialized.NotifyCollectionChangedEventHandler.Invoke(Object sender, NotifyCollectionChangedEventArgs e)
   at System.Collections.ObjectModel.ObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e)
   at System.Collections.ObjectModel.ObservableCollection`1.ClearItems()
   at Syncfusion.UI.Xaml.Gauges.SfCircularGauge.Dispose()
   at System.Windows.Navigation.DisposeTreeQueueItem.DisposeElement(Object node)
   at System.Windows.Navigation.DisposeTreeQueueItem.DisposeElement(Object node)
   at System.Windows.Navigation.DisposeTreeQueueItem.DisposeElement(Object node)
   at System.Windows.Navigation.DisposeTreeQueueItem.DisposeElement(Object node)
   at System.Windows.Navigation.DisposeTreeQueueItem.DisposeElement(Object node)
   at System.Windows.Navigation.DisposeTreeQueueItem.DisposeElement(Object node)
   at System.Windows.Navigation.DisposeTreeQueueItem.Dispatch(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)

Xaml:

<syncfusion:SfCircularGauge x:Name="gauge3" Margin="5" Background="Transparent" Grid.Column="1" HeaderAlignment="Bottom" BorderThickness="1" BorderBrush="White"  >
                    <syncfusion:SfCircularGauge.GaugeHeader>
                        <TextBlock Text="{Binding FluidicsStatus.HighVacuumStatus.VacuumPsi, StringFormat={}{0:F2} kPa, FallbackValue=0.0 kPa}"  Height="40" Width="auto" FontSize="18" Foreground="Black"/>
                    </syncfusion:SfCircularGauge.GaugeHeader>
                    <syncfusion:SfCircularGauge.Scales>
                        <syncfusion:CircularScale  MajorTickOffset="0.4" MinorTickOffset="0.4" LabelOffset="0.5" RimStroke="Maroon" TickStroke="{StaticResource ForegroundBrush}" SmallTickStroke="{StaticResource ForegroundBrush}"  SmallTickLength="8" RimStrokeThickness="5"
                                          LabelStroke="{StaticResource ForegroundBrush}" FontSize="14" FontWeight="SemiBold"  SmallTickStrokeThickness="2" SweepDirection="Counterclockwise"
                                          Interval="5" MinorTicksPerInterval="2" TickLength="20" TickStrokeThickness="1" BindRangeStrokeToLabels="False" BindRangeStrokeToTicks="False"
                                          StartAngle="45" SweepAngle="270" StartValue="{Binding FluidicsStatus.HighVacuumStatus.ManageParams.ErrorWeakKPa}" EndValue="{Binding FluidicsStatus.HighVacuumStatus.ManageParams.ErrorStrongKPa}" >
                            <syncfusion:CircularScale.Ranges>
                                <syncfusion:CircularRange StartValue="{Binding FluidicsStatus.HighVacuumStatus.ManageParams.WeakKPa}" EndValue="{Binding FluidicsStatus.HighVacuumStatus.ManageParams.TargetKPa}"  Stroke="DarkGreen"  />
                            </syncfusion:CircularScale.Ranges>
                            <syncfusion:CircularScale.Pointers>
                                <syncfusion:CircularPointer EnableAnimation="True" PointerCapDiameter="20" PointerType="NeedlePointer" NeedlePointerStroke="LightSkyBlue" NeedlePointerStrokeThickness="5" NeedleLengthFactor="0.8" PointerCapStroke="#414d4f" Value="{Binding FluidicsStatus.HighVacuumStatus.VacuumPsi}"/>
                            </syncfusion:CircularScale.Pointers>
                        </syncfusion:CircularScale>
                    </syncfusion:SfCircularGauge.Scales>
                </syncfusion:SfCircularGauge>

Hi Grant, 

 

Greetings from Syncfusion. We have checked the reported scenario with our end and we were able to reproduce the reported issue. We have logged a defect report for this and the fix will be available in our upcoming Volume 4 release which is expected to be roll out on mid of December 2018. 

 

Regards, 

Muneesh Kumar G.