Exception in DoubleUpDown control when the Value property isn't bound to anything

[andyste1]

I have a view model that exposes a property which is bound to the Value property of a DoubleUpDown control. In some scenarios this view model can be null, which results in the exception shown below.
The exception occurs in a .Net6 solution using DotNetProjects.Extended.Wpf.Toolkit v5.0.103. This solution was recently migrated from a .Net 4.x solution (using Extended.Wpf.Toolkit 2.9.0), where we experience no exceptions when the VM is null.

System.NullReferenceException: Object reference not set to an instance of an object. at Xceed.Wpf.Toolkit.CommonNumericUpDown1.ConvertValueToText()
at Xceed.Wpf.Toolkit.Primitives.UpDownBase1.SyncTextAndValueProperties(Boolean updateValueFromText, String text, Boolean forceTextUpdate) at Xceed.Wpf.Toolkit.Primitives.UpDownBase1.OnValueChanged(T oldValue, T newValue)
at Xceed.Wpf.Toolkit.Primitives.UpDownBase1.OnValueChanged(DependencyObject o, 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, Boolean preserveCurrentValue) at System.Windows.DependencyObject.InvalidateProperty(DependencyProperty dp) 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.AttachToContext(AttachAttempt attempt) at System.Windows.Data.BindingExpression.MS.Internal.Data.IDataBindEngineClient.AttachToContext(Boolean lastChance) at MS.Internal.Data.DataBindEngine.Task.Run(Boolean lastChance) at MS.Internal.Data.DataBindEngine.Run(Object arg) at MS.Internal.Data.DataBindEngine.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.FireInvokeOnRenderCallbacks() at System.Windows.Media.MediaContext.RenderMessageHandlerCore(Object resizedCompositionTarget) at System.Windows.Media.MediaContext.RenderMessageHandler(Object resizedCompositionTarget) at System.Windows.Media.MediaContext.Resize(ICompositionTarget 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)

If I add FallbackValue=0 to the Value binding of the control then I see a slightly different exception:

System.NullReferenceException: Object reference not set to an instance of an object. at Xceed.Wpf.Toolkit.CommonNumericUpDown1.ConvertValueToText()
at Xceed.Wpf.Toolkit.Primitives.UpDownBase1.SyncTextAndValueProperties(Boolean updateValueFromText, String text, Boolean forceTextUpdate) at Xceed.Wpf.Toolkit.NumericUpDown1.OnFormatStringChanged(String oldValue, String newValue)
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.DependencyObject.InvalidateProperty(DependencyProperty dp)
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.AttachToContext(AttachAttempt attempt)
at System.Windows.Data.BindingExpression.MS.Internal.Data.IDataBindEngineClient.AttachToContext(Boolean lastChance)
at MS.Internal.Data.DataBindEngine.Task.Run(Boolean lastChance)
at MS.Internal.Data.DataBindEngine.Run(Object arg)
at MS.Internal.Data.DataBindEngine.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.FireInvokeOnRenderCallbacks()
at System.Windows.Media.MediaContext.RenderMessageHandlerCore(Object resizedCompositionTarget)
at System.Windows.Media.MediaContext.RenderMessageHandler(Object resizedCompositionTarget)
at System.Windows.Media.MediaContext.Resize(ICompositionTarget 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)`

And if I add FallbackValue=F0 to the FormatString= property (which is also bound to a property on my VM) then that makes no difference and still see the latter exception.

[andyste1]

I've now switched to the Xceed Extended.Wpf.Toolkit (4.4.0) and the problem has gone away.