WPF-Bindung mit angegebenem Typ (ItemTemplate)

Question

Ich habe eine ListBox in meiner WPF-Anwendung, für die ich ein benutzerdefiniertes ItemTemplate erstellen möchte.

Als ich den Typ des ListBoxItem angeben, wenn in der Vorlage, um seine Eigenschaften zu binden, bekam ich die folgende Ausnahme:

Code:

<ListBox SelectionMode="Multiple" ItemsSource="{Binding CashTypes}" IsSynchronizedWithCurrentItem="True"> 
    <ListBox.ItemContainerStyle> 
     <Style TargetType="{x:Type ListBoxItem}" BasedOn="{StaticResource {x:Type ListBoxItem}}"> 
      <Setter Property="IsSelected" Value="{Binding Mode=TwoWay, Path=(local:CashTypeEnumViewModel.IsSelected)}"/> 
     </Style> 
    </ListBox.ItemContainerStyle> 
    <ListBox.ItemTemplate> 
     <DataTemplate> 
      <TextBlock Text="{Binding (local:CashTypeEnumViewModel.CashType)}"></TextBlock> 
     </DataTemplate> 
    </ListBox.ItemTemplate> 
</ListBox> 

Ausnahme:

System.Windows.Markup.XamlParseException occurred 
    HResult=-2146233087 
    LineNumber=0 
    LinePosition=0 
    Message=Key cannot be null. 
Parameter name: key 
    Source=PresentationFramework 
    StackTrace: 
     at System.Windows.FrameworkTemplate.LoadTemplateXaml(XamlReader templateReader, XamlObjectWriter currentWriter) 
     at System.Windows.FrameworkTemplate.LoadTemplateXaml(XamlObjectWriter objectWriter) 
     at System.Windows.FrameworkTemplate.LoadOptimizedTemplateContent(DependencyObject container, IComponentConnector componentConnector, IStyleConnector styleConnector, List`1 affectedChildren, UncommonField`1 templatedNonFeChildrenField) 
     at System.Windows.FrameworkTemplate.LoadContent(DependencyObject container, List`1 affectedChildren) 
     at System.Windows.StyleHelper.ApplyTemplateContent(UncommonField`1 dataField, DependencyObject container, FrameworkElementFactory templateRoot, Int32 lastChildIndex, HybridDictionary childIndexFromChildID, FrameworkTemplate frameworkTemplate) 
     at System.Windows.FrameworkTemplate.ApplyTemplateContent(UncommonField`1 templateDataField, FrameworkElement container) 
     at System.Windows.FrameworkElement.ApplyTemplate() 
     at System.Windows.FrameworkElement.MeasureCore(Size availableSize) 
     at System.Windows.UIElement.Measure(Size availableSize) 
     at System.Windows.Controls.Border.MeasureOverride(Size constraint) 
     at System.Windows.FrameworkElement.MeasureCore(Size availableSize) 
     at System.Windows.UIElement.Measure(Size availableSize) 
     at System.Windows.Controls.Control.MeasureOverride(Size constraint) 
     at System.Windows.FrameworkElement.MeasureCore(Size availableSize) 
     at System.Windows.UIElement.Measure(Size availableSize) 
     at System.Windows.Controls.VirtualizingStackPanel.MeasureChild(IItemContainerGenerator& generator, IContainItemStorage& itemStorageProvider, IContainItemStorage& parentItemStorageProvider, Object& parentItem, Boolean& hasUniformOrAverageContainerSizeBeenSet, Double& computedUniformOrAverageContainerSize, Double& computedUniformOrAverageContainerPixelSize, Boolean& computedAreContainersUniformlySized, IList& items, Object& item, IList& children, Int32& childIndex, Boolean& visualOrderChanged, Boolean& isHorizontal, Size& childConstraint, Rect& viewport, VirtualizationCacheLength& cacheSize, VirtualizationCacheLengthUnit& cacheUnit, Boolean& foundFirstItemInViewport, Double& firstItemInViewportOffset, Size& stackPixelSize, Size& stackPixelSizeInViewport, Size& stackPixelSizeInCacheBeforeViewport, Size& stackPixelSizeInCacheAfterViewport, Size& stackLogicalSize, Size& stackLogicalSizeInViewport, Size& stackLogicalSizeInCacheBeforeViewport, Size& stackLogicalSizeInCacheAfterViewport, Boolean& mustDisableVirtualization, Boolean isBeforeFirstItem, Boolean isAfterFirstItem, Boolean isAfterLastItem, Boolean skipActualMeasure, Boolean skipGeneration, Boolean& hasBringIntoViewContainerBeenMeasured, Boolean& hasVirtualizingChildren) 
     at System.Windows.Controls.VirtualizingStackPanel.MeasureOverrideImpl(Size constraint, Nullable`1& lastPageSafeOffset, List`1& previouslyMeasuredOffsets, Nullable`1& lastPagePixelSize, Boolean remeasure) 
     at System.Windows.Controls.VirtualizingStackPanel.MeasureOverride(Size constraint) 
     at System.Windows.FrameworkElement.MeasureCore(Size availableSize) 
     at System.Windows.UIElement.Measure(Size availableSize) 
     at System.Windows.ContextLayoutManager.UpdateLayout() 
     at System.Windows.UIElement.UpdateLayout() 
     at System.Windows.Interop.HwndSource.SetLayoutSize() 
     at System.Windows.Interop.HwndSource.set_RootVisualInternal(Visual value) 
     at System.Windows.Interop.HwndSource.set_RootVisual(Visual value) 
     at System.Windows.Window.SetRootVisual() 
     at System.Windows.Window.SetRootVisualAndUpdateSTC() 
     at System.Windows.Window.SetupInitialState(Double requestedTop, Double requestedLeft, Double requestedWidth, Double requestedHeight) 
     at System.Windows.Window.CreateSourceWindow(Boolean duringShow) 
     at System.Windows.Window.CreateSourceWindowDuringShow() 
     at System.Windows.Window.SafeCreateWindowDuringShow() 
     at System.Windows.Window.ShowHelper(Object booleanBox) 
     at System.Windows.Window.Show() 
     at XY.ApplicationBootstrapper.InitializeShell() in C:\_git\XY\Startup\ApplicationBootstrapper.cs:line 85 
    InnerException: 
     HResult=-2147467261 
     Message=Key cannot be null. 
Parameter name: key 
     ParamName=key 
     Source=System 
     StackTrace: 
      at System.Collections.Specialized.ListDictionary.get_Item(Object key) 
      at System.Collections.Specialized.HybridDictionary.get_Item(Object key) 
      at System.ComponentModel.PropertyChangedEventManager.AddListener(INotifyPropertyChanged source, String propertyName, IWeakEventListener listener, EventHandler`1 handler) 
      at System.ComponentModel.PropertyChangedEventManager.AddHandler(INotifyPropertyChanged source, EventHandler`1 handler, String propertyName) 
      at MS.Internal.Data.PropertyPathWorker.ReplaceItem(Int32 k, Object newO, Object parent) 
      at MS.Internal.Data.PropertyPathWorker.UpdateSourceValueState(Int32 k, ICollectionView collectionView, Object newValue, Boolean isASubPropertyChange) 
      at MS.Internal.Data.ClrBindingWorker.AttachDataItem() 
      at System.Windows.Data.BindingExpression.Activate(Object item) 
      at System.Windows.Data.BindingExpression.AttachToContext(AttachAttempt attempt) 
      at System.Windows.Data.BindingExpression.AttachOverride(DependencyObject target, DependencyProperty dp) 
      at System.Windows.Data.BindingExpressionBase.OnAttach(DependencyObject d, DependencyProperty dp) 
      at System.Windows.StyleHelper.GetInstanceValue(UncommonField`1 dataField, DependencyObject container, FrameworkElement feChild, FrameworkContentElement fceChild, Int32 childIndex, DependencyProperty dp, Int32 i, EffectiveValueEntry& entry) 
      at System.Windows.StyleHelper.GetChildValueHelper(UncommonField`1 dataField, ItemStructList`1& valueLookupList, DependencyProperty dp, DependencyObject container, FrameworkObject child, Int32 childIndex, Boolean styleLookup, EffectiveValueEntry& entry, ValueLookupType& sourceType, FrameworkElementFactory templateRoot) 
      at System.Windows.StyleHelper.GetChildValue(UncommonField`1 dataField, DependencyObject container, Int32 childIndex, FrameworkObject child, DependencyProperty dp, FrugalStructList`1& childRecordFromChildIndex, EffectiveValueEntry& entry, ValueLookupType& sourceType, FrameworkElementFactory templateRoot) 
      at System.Windows.StyleHelper.GetValueFromTemplatedParent(DependencyObject container, Int32 childIndex, FrameworkObject child, DependencyProperty dp, FrugalStructList`1& childRecordFromChildIndex, FrameworkElementFactory templateRoot, EffectiveValueEntry& entry) 
      at System.Windows.StyleHelper.ApplyTemplatedParentValue(DependencyObject container, FrameworkObject child, Int32 childIndex, FrugalStructList`1& childRecordFromChildIndex, DependencyProperty dp, FrameworkElementFactory templateRoot) 
      at System.Windows.StyleHelper.InvalidatePropertiesOnTemplateNode(DependencyObject container, FrameworkObject child, Int32 childIndex, FrugalStructList`1& childRecordFromChildIndex, Boolean isDetach, FrameworkElementFactory templateRoot) 
      at System.Windows.FrameworkTemplate.InvalidatePropertiesOnTemplate(DependencyObject container, Object currentObject) 
      at System.Windows.FrameworkTemplate.HandleBeforeProperties(Object createdObject, DependencyObject& rootObject, DependencyObject container, FrameworkElement feContainer, INameScope nameScope) 
      at System.Windows.FrameworkTemplate.<>c__DisplayClass45_0.<LoadOptimizedTemplateContent>b__2(Object sender, XamlObjectEventArgs args) 
      at System.Xaml.XamlObjectWriter.OnBeforeProperties(Object value) 
      at System.Xaml.XamlObjectWriter.Logic_CreateAndAssignToParentStart(ObjectWriterContext ctx) 
      at System.Xaml.XamlObjectWriter.WriteEndObject() 
      at System.Xaml.XamlWriter.WriteNode(XamlReader reader) 
      at System.Windows.FrameworkTemplate.LoadTemplateXaml(XamlReader templateReader, XamlObjectWriter currentWriter) 
     InnerException: 

Wie Solange ich den Typ nicht festlege, funktioniert alles ...

Code:

<ListBox SelectionMode="Multiple" ItemsSource="{Binding CashTypes}" IsSynchronizedWithCurrentItem="True"> 
    <ListBox.ItemContainerStyle> 
     <Style TargetType="{x:Type ListBoxItem}" BasedOn="{StaticResource {x:Type ListBoxItem}}"> 
      <Setter Property="IsSelected" Value="{Binding Mode=TwoWay, Path=(local:CashTypeEnumViewModel.IsSelected)}"/> 
     </Style> 
    </ListBox.ItemContainerStyle> 
    <ListBox.ItemTemplate> 
     <DataTemplate> 
      <TextBlock Text="{Binding CashType}"></TextBlock> 
     </DataTemplate> 
    </ListBox.ItemTemplate> 
</ListBox> 

Wie kann ich es mit dem angegebenen Typ arbeiten lassen?

Answer 1

richtige Ort für Typ DataType Eigentum von Datatemplate

ist

<DataTemplate DataType="{x:Type local:CashTypeEnumViewModel}> 
    <TextBlock Text="{Binding CashType}"/> 
</DataTemplate>