Wpf 如何从TabControl获取TabPanel实际宽度

我有一个选项卡控件，选项卡条放置在左侧。因此，它是一个简单的导航菜单类型选项卡控件。 TabControl的控件模板中有一个TabPanel

<ControlTemplate TargetType="{x:Type TabControl}">
       <Grid x:Name="Grid" ClipToBounds="true" SnapsToDevicePixels="true" KeyboardNavigation.TabNavigation="Local">
               <Grid.ColumnDefinitions>
                   <ColumnDefinition x:Name="ColumnDefinition0"/>
                   <ColumnDefinition x:Name="ColumnDefinition1" Width="0"/>
               </Grid.ColumnDefinitions>
               <Grid.RowDefinitions>
                   <RowDefinition x:Name="RowDefinition0" Height="Auto"/>
                   <RowDefinition x:Name="RowDefinition1" Height="*"/>
               </Grid.RowDefinitions>
               <Border x:Name="ContentPanel" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Grid.Column="0" KeyboardNavigation.DirectionalNavigation="Contained" Grid.Row="1" KeyboardNavigation.TabIndex="2" KeyboardNavigation.TabNavigation="Local" Padding="{TemplateBinding Padding}" Margin="0,-1,0,0">
                   <ContentPresenter x:Name="PART_SelectedContentHost" ContentSource="SelectedContent" Margin="{TemplateBinding Padding}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
               </Border>
               <ScrollViewer x:Name="scroll" VerticalScrollBarVisibility="Disabled" HorizontalScrollBarVisibility="Auto" Template="{StaticResource ScrollViewerTab}">
                   <TabPanel x:Name="HeaderPanel" IsItemsHost="true" Margin="0,2,0,0" KeyboardNavigation.TabIndex="1" Panel.ZIndex="1" VerticalAlignment="Bottom" />
               </ScrollViewer>
           </Grid>
    </ControlTemplate>

为了对齐，我需要TabPanel（选项卡标题）的实际宽度在tabcontrol之外

我试着跟着，但没用

<TextBlock Text="{Binding Path=Actualwidth, ElementName=HeaderPanel}" />
<TabControl />

<TabControl Tag="{Binding Path=ActualWidth, ElementName=HeaderPanel}" />

我还尝试将header面板的ActualWidth绑定到TabControl的Tag属性。即使这样也不行

<TextBlock Text="{Binding Path=Actualwidth, ElementName=HeaderPanel}" />
<TabControl />

<TabControl Tag="{Binding Path=ActualWidth, ElementName=HeaderPanel}" />

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TabControls.Items集合提供ViewModel对象的列表。因此我无法获取TabItem实例。

我最终在codebehind文件中使用了visual tree helper

var tabPanel = VisualTreeHelpers.FindChild<TabPanel>(TabControl, "MenuPanel");

var tabPanel=visualtreehelopers.FindChild（TabControl，“MenuPanel”）；