TabItem的ContextMenu命令绑定失效问题

[saybookcat]

实现如下：

  <ControlTemplate x:Key="TabControlContentTemplate" TargetType="{x:Type TabControl}">
		<Grid>
			<Grid.RowDefinitions>
				<RowDefinition Height="Auto" />
				<RowDefinition Height="*" />
			</Grid.RowDefinitions>
			<ScrollViewer Grid.Row="0"
						  x:Name="TabControlScroller"
						  VerticalScrollBarVisibility="Disabled"
						  HorizontalScrollBarVisibility="Auto"
						  Style="{StaticResource TabHeaderScrollViewer}">
				<TabPanel IsItemsHost="True" SnapsToDevicePixels="True" />
			</ScrollViewer>
			<Border Grid.Row="1" BorderBrush="{StaticResource DefaultBrush}" BorderThickness="1">
				<ContentPresenter ContentSource="SelectedContent" />
			</Border>
		</Grid>
	</ControlTemplate>


	<Style TargetType="TabItem" x:Key="TabItemStyle">
		<Setter Property="Margin" Value="0,3,0,0" />
		<Setter Property="Height" Value="Auto" />
		<Setter Property="MaxWidth" Value="300" />
		<Setter Property="Padding" Value="5" />
		<Setter Property="HorizontalAlignment" Value="Stretch" />
		<Setter Property="VerticalAlignment" Value="Stretch" />
		<Setter Property="HorizontalContentAlignment" Value="Stretch" />
		<Setter Property="VerticalContentAlignment" Value="Stretch" />
		<Setter Property="SnapsToDevicePixels" Value="True" />
		<Setter Property="HeaderTemplate">
			<Setter.Value>
				<DataTemplate>
					<Grid Focusable="False" VerticalAlignment="Center"  >
						<Grid.ColumnDefinitions>
							<ColumnDefinition Width="Auto" />
							<ColumnDefinition Width="*" />
							<ColumnDefinition Width="Auto" />

						</Grid.ColumnDefinitions>
						<Image Grid.Column="0"
							   Focusable="False"
							   Width="16" Height="16" Margin="3,0,3,0"
							   Source="{Binding TabImageSource}" />
						<ContentPresenter
							Focusable="False"
							Grid.Column="1"
							x:Name="ContentSite"
							VerticalAlignment="Center"
							HorizontalAlignment="Center"
							ContentSource="Header"
							Margin="0,3,0,3"
							Content="{Binding TabName}" />

						<Button x:Name="CloseButton"
								Grid.Column="2"
								VerticalAlignment="Center"
								HorizontalAlignment="Center"
								Margin="5,0,5,0"
								Style="{StaticResource CloseButtonStyle}"
								Visibility="Visible"
								Command="{Binding DataContext.TabItemViewModel.TabItemCloseCmd,RelativeSource={RelativeSource AncestorType={x:Type TabControl}}}"
								CommandParameter="{Binding}" />
					</Grid>
				</DataTemplate>
			</Setter.Value>
		</Setter>
	   <Setter Property="ContextMenu">
			<Setter.Value>
				<ContextMenu Margin="0,0,0.4,0">
					<MenuItem Header="关闭"
					 Command="{Binding DataContext.TabItemViewModel.CloseTabCmd,RelativeSource={RelativeSource FindAncestor,AncestorType={x:Type ContextMenu}}}"
					
				  />

					<MenuItem Header="关闭所有页面"
				  Command="{Binding DataContext.TabItemViewModel.CloseAllTabCmd,RelativeSource={RelativeSource FindAncestor,AncestorType={x:Type ContextMenu}}}"
				  CommandParameter="{Binding Path=PlacementTarget.Parent, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type ContextMenu}}}" />

					<MenuItem Header="除此之外全部关闭"
				  Command="{Binding DataContext.TabItemViewModel.CloseOtherTabCmd,RelativeSource={RelativeSource AncestorType={x:Type ContextMenu}}}"
				  CommandParameter="{Binding Path=PlacementTarget.Parent, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type ContextMenu}}}" />
				</ContextMenu>
			</Setter.Value>
		</Setter>

		<Setter Property="Content" Value="{Binding UserControl}" />

<TabControl 
                        Name="tabControl"
                        ItemsSource="{Binding TabItemViewModel.TabItems}"
                        SelectedItem="{Binding TabItemViewModel.SelectedModel,Mode=TwoWay}"
                        ItemContainerStyle="{StaticResource TabItemStyle}"
                        Template="{StaticResource TabControlContentTemplate}">
           
            </TabControl>

右键菜单的命令点击失效，无法寻找到TabItemViewModel中的CloseTabCmd等命令，如要如何binding才能生效？

[exception92]

Command="{Binding DataContext.TabItemViewModel.CloseTabCmd,RelativeSource={RelativeSource FindAncestor,AncestorType={x:Type ContextMenu}}}" -》AncestorType 类型不应该是ContextMenu，因为它没有DataContext指定，应该是TabControl级别的