Wpf Treeview Contextmenu DataContext

Question

I am trying to set the Datacontext of my Contextmenu - but my Code does not work. Very similar code works at another location, so I would be grateful if somebody could explain why it does not work.

My Treeview looks like this: Beware: it is rather long, but I think the nested structure is part of the problem, so I do want to shrink it. The Problem occurs on the second "level" at the ppChart Binding.

    <TreeView x:Name ="Presentation_SlidesWithIndex" Grid.ColumnSpan="1" HorizontalAlignment="stretch" Height="auto" Margin="0,0,3,0" VerticalAlignment="stretch" Width="auto" Tag="{Binding DataContext, ElementName=LayoutRoot}">
        <TreeView.ItemContainerStyle>
            <!--expand Charts when they contain elements-->
            <Style TargetType="TreeViewItem">
                <Setter Property="IsExpanded" Value="{Binding HasCharts}"/>
            </Style>
        </TreeView.ItemContainerStyle>

        <TreeView.Resources>
            <HierarchicalDataTemplate DataType="{x:Type pp:PPSlide}" ItemsSource="{Binding Charts}">
                <StackPanel x:Name="PPSlideElements" Orientation="Horizontal">
                    <StackPanel.Style>
                        <Style TargetType="{x:Type StackPanel}">
                            <Style.Triggers>
                                <!--Trigger for Slides with Charts-->
                                <DataTrigger Binding="{Binding Path=HasCharts}"  Value="True" >
                                    <Setter Property="Background" Value="LightBlue" />
                                </DataTrigger>
                                <!--Trigger for Slides with NO Charts-->
                                <DataTrigger Binding="{Binding Path=HasCharts}"  Value="False" >
                                    <Setter Property="Opacity" Value=".5" />
                                </DataTrigger>
                            </Style.Triggers>
                        </Style>
                    </StackPanel.Style>
                    <TextBlock FontSize="15">
                        <Run Text="Slide "></Run>
                        <Run Text="{Binding Path=Index}"></Run>
                    </TextBlock>
                    <!--<Image Source="/Images/pptIcon.png" Height="10"></Image>-->
                </StackPanel>
            </HierarchicalDataTemplate>
            <HierarchicalDataTemplate DataType="{x:Type pp:PPChart}" ItemsSource="{Binding ExcelSource}">
                <StackPanel x:Name="PpChartElements" Orientation="Horizontal" AllowDrop="True" cal:Message.Attach="[Event Drop] = [Action DropItem($eventArgs,$view)]" Tag="{Binding DataContext, RelativeSource={RelativeSource AncestorType=UserControl}}">
                    <StackPanel.Style>
                        <Style TargetType="{x:Type StackPanel}">
                            <Style.Triggers>
                                <!--Trigger for Charts with DataSource set-->
                                <DataTrigger Binding="{Binding Path=HasDataSourceSet}"  Value="True" >
                                    <Setter Property="Background" Value="LightGreen" />
                                </DataTrigger>
                                <!--Trigger for Charts with DataSource nit set-->
                                <DataTrigger Binding="{Binding Path=HasDataSourceSet}"  Value="False" >
                                    <Setter Property="Background" Value="Orange" />
                                </DataTrigger>
                            </Style.Triggers>
                        </Style>
                    </StackPanel.Style>
                    <Image Source="{Binding ChartType, Converter={StaticResource PowerPointChartTypeConverter}}" Width="19" Height="19" Margin="2,2,4,2"></Image>
                    <TextBlock  FontSize="14" Text="{Binding Path=ShapeName}" VerticalAlignment="Center">
                        <TextBlock.ContextMenu>
                            <ContextMenu cal:Action.TargetWithoutContext="{Binding Path=PlacementTarget.Tag.AddEntityCommand, RelativeSource={RelativeSource AncestorType=ContextMenu}}">
                                <MenuItem Header="Löse Verknüpfung" cal:Message.Attach="DeleteLink($datacontext)" ToolTip="Löscht einen bestehenden Link zu einer Excel Datei"/>
                            </ContextMenu>
                        </TextBlock.ContextMenu>
                    </TextBlock>
                    <Image Source="{Binding PowerPointWriteStatus, Converter={StaticResource PowerPointWriteStatusConverter}}" Width="19" Height="19" Margin="2,2,4,2" ToolTip="Zeigt erfolg oder misserfolg des Erstellens an"></Image>
                </StackPanel>
            </HierarchicalDataTemplate>
            <HierarchicalDataTemplate DataType="{x:Type pp:PPSourceExcelLink}">
                <StackPanel x:Name="PpSourceExcelLinkStackPanel" Orientation="Vertical">
                    <TextBlock FontSize="14">
                        <Run Text="Datei: "></Run>
                        <Run Text="{Binding Path=ExcelFileName, Mode=OneWay}"></Run>
                    </TextBlock>
                    <TextBlock FontSize="14">
                        <Run Text="Tabelle: "></Run>
                        <Run Text="{Binding Path=SourceTableID}"></Run>
                    </TextBlock>
                </StackPanel>
            </HierarchicalDataTemplate>

        </TreeView.Resources>
    </TreeView>

Answer 1

As stated in RelativeSource binding from a ToolTip or ContextMenu there is no need to add the tag to the PlacementTarget. This makes it shorter, as there is no need to add a tag to the control and to the binding path of the ContextMenu, e.g.:

<TextBlock FontSize="14" Text="{Binding Path=ShapeName}" VerticalAlignment="Center">
    <TextBlock.ContextMenu>
        <ContextMenu cal:Action.TargetWithoutContext="{Binding Path=PlacementTarget, RelativeSource={RelativeSource Self}}">
            <MenuItem Header="Löse Verknüpfung" cal:Message.Attach="DeleteLink($datacontext)" ToolTip="Löscht einen bestehenden Link zu einer Excel Datei" />
        </ContextMenu>
    </TextBlock.ContextMenu>
</TextBlock>

and in the ViewModel

public void DeleteLink(object parameter)
{
    if (parameter == null)
        return;
    var param = parameter as YourDataContextType;
    if (! (param is YourDataContextType))
        return;

    // your delete handling
}

Answer 2

I found a Solution which works fairly well - but why it works is beyond me:

<TextBlock FontSize="14" Text="{Binding Path=ShapeName}" VerticalAlignment="Center" Tag="{Binding DataContext, RelativeSource={AncestorType=TreeView}}">
    <TextBlock.ContextMenu>
        <ContextMenu cal:Action.TargetWithoutContext="{Binding RelativeSource={RelativeSource Self},Path=PlacementTarget.Tag}">
            <MenuItem Header="Löse Verknüpfung" cal:Message.Attach="DeleteLink($datacontext)" ToolTip="Löscht einen bestehenden Link zu einer Excel Datei" />
        </ContextMenu>
    </TextBlock.ContextMenu>
</TextBlock>

Note how the Ancestertype treeview is used. my bet guess is that it walks the Visual tree until it finds the Treeview, which has the proper DataContect. Thanks to Sniffer, which did a very good job !

Answer 3

I think your problem lies exactly in this line of code:

cal:Action.TargetWithoutContext="{Binding Path=PlacementTarget.Tag.AddEntityCommand, RelativeSource={RelativeSource AncestorType=ContextMenu}}"

To fix it you need to change this to:

cal:Action.TargetWithoutContext="{Binding Path=PlacementTarget.Tag.AddEntityCommand, RelativeSource={RelativeSource Self}}"

but this alone won't fix your problem because the target of the action message will be the TextBlock which doesn't have its Tag property set.

Anyway you should end up with code similar to this:

<TextBlock FontSize="14" Text="{Binding Path=ShapeName}" VerticalAlignment="Center" Tag="{Binding DataContext, RelativeSource={RelativeSource Self}}">
    <TextBlock.ContextMenu>
        <ContextMenu cal:Action.TargetWithoutContext="{Binding RelativeSource={RelativeSource Self},Path=PlacementTarget.Tag}">
            <MenuItem Header="Löse Verknüpfung" cal:Message.Attach="DeleteLink($datacontext)" ToolTip="Löscht einen bestehenden Link zu einer Excel Datei" />
        </ContextMenu>
    </TextBlock.ContextMenu>
</TextBlock>

I answered a similar question recently and you can take a look at for more details.