Using Visual Studio 2013, C# and WPF.
I have a simple User Control when used in a window causes: "NullReferenceException: Object reference not set to an instance of an object."
However when code is executed it works as expected.
at Slakt004.UCDateFlat.DateType_SelectionChanged(Object sender, SelectionChangedEventArgs e)
at System.Windows.Controls.SelectionChangedEventArgs.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.RaiseEvent(RoutedEventArgs e)
at System.Windows.Controls.ComboBox.OnSelectionChanged(SelectionChangedEventArgs e)
at System.Windows.Controls.Primitives.Selector.InvokeSelectionChanged(List`1 unselectedInfos, List`1 selectedInfos)
at System.Windows.Controls.Primitives.Selector.SelectionChanger.End()
at System.Windows.Controls.Primitives.Selector.SelectionChanger.SelectJustThisItem(ItemInfo info, Boolean assumeInItemsCollection)
at System.Windows.Controls.Primitives.Selector.OnSelectedItemChanged(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.Selector.OnItemsChanged(NotifyCollectionChangedEventArgs e)
at System.Windows.Controls.ItemsControl.OnItemCollectionChanged2(Object sender, NotifyCollectionChangedEventArgs e)
at System.Collections.Specialized.NotifyCollectionChangedEventHandler.Invoke(Object sender, NotifyCollectionChangedEventArgs e)
at System.Windows.Data.CollectionView.OnCollectionChanged(NotifyCollectionChangedEventArgs args)
at System.Windows.Controls.ItemCollection.OnViewCollectionChanged(Object sender, NotifyCollectionChangedEventArgs e)
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.CollectionChangedEventManager.OnCollectionChanged(Object sender, NotifyCollectionChangedEventArgs args)
at System.Windows.Data.CollectionView.OnCollectionChanged(NotifyCollectionChangedEventArgs args)
at System.Windows.Data.ListCollectionView.RefreshOverride()
at System.Windows.Data.CollectionView.RefreshInternal()
at System.Windows.Data.CollectionView.Refresh()
at System.Windows.Data.CollectionView.EndDefer()
at System.Windows.Data.CollectionView.DeferHelper.Dispose()
at System.Windows.Controls.ItemCollection.SetCollectionView(CollectionView view)
at System.Windows.Controls.ItemCollection.SetItemsSource(IEnumerable value, Func`2 GetSourceItem)
at System.Windows.Controls.ItemsControl.OnItemsSourceChanged(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, 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.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.UIElement.UpdateLayout()
Slakt004.UCDateFlat.DateType_SelectionChanged(Object sender, SelectionChangedEventArgs e) looks as follows:
private void DateType_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
DateType.Width = 35;
if (DateType.SelectedItem != null)
{
DateTypeDef selectedDateType = DateType.SelectedItem as DateTypeDef;
source.DateType = selectedDateType.Id;
//If changed to "between" no update should be done here of if year = 0 or when toYear is to small
//the event will be created when toYear is updated
if (selectedDateType.Id != Enumerations.between)
{
//Generate an event
UCDateUpdateEventArgs args = new UCDateUpdateEventArgs(source);
UCDateUpdated(this, args);
}
else
{
if (source.YearTo >= source.Year)
{
//Generate an event
UCDateUpdateEventArgs args = new UCDateUpdateEventArgs(source);
UCDateUpdated(this, args);
}
}
}
}
If I comment out the event triggers then Visual Studio is able to show the design view of the window.
None of the tips I have found when searching has helped. Any tips are welcome!