wpf - WPF 绑定问题

Question

我正在尝试自定义控件TreeView。当用户在 中选择一个项目时TreeView，我需要将ActualWidth的SelectedItem存储在项目的标签中：

 <Style x:Key="{x:Type TreeViewItem}" TargetType="{x:Type TreeViewItem}">
           <!-- ... -->
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type TreeViewItem}">
                        <Grid ShowGridLines="True">

                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="Auto" />
                                <ColumnDefinition />
                            </Grid.ColumnDefinitions>
                            <Grid.RowDefinitions>
                                <RowDefinition />
                                <RowDefinition />
                            </Grid.RowDefinitions>

                            <Rectangle x:Name="rect" />

                            <ContentPresenter x:Name="PART_Header" ContentSource="Header" Margin="5" />         

                            <ItemsPresenter x:Name="ItemsHost" Grid.Row="1" Grid.Column="1" />
                            <!-- ... -->       
                        </Grid>

                        <ControlTemplate.Triggers>
                            <Trigger Property="IsSelected" Value="true">
                                <Setter Property="Tag" Value="{Binding ElementName=rect, Path=ActualWidth}" />
                            </Trigger>
                        </ControlTemplate.Triggers>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>

后来，我听了以下SelectedItemChanged事件TreeView：

private void views_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
    {
        TreeViewItem item = (TreeViewItem)e.NewValue;
        double i = (double)item.Tag;
    }

现在的问题是 item.Tag 始终为空。这是我绑定的问题吗？还是应该以不同的方式做事？

Answer 1

试试看：

<Setter Property="Tag" Value="{Binding Path=ActualWidth, RelativeSource={x:Static RelativeSource.Self}}" />