带GridSplitter的WPF扩展器

在我的WPF窗口（.NET 4.0）中，网格包含两列：左侧的拉伸文本框（或其他内容）和右侧的Expander。同样在Expander中，我有GridSplitter，它用于在Expander扩展时调整左右列的大小。但这是行不通的。

这是我的XAML代码：

<Window x:Class="WpfApplication10.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="350" Width="525">
<Grid ShowGridLines="True" >
    <Grid.ColumnDefinitions>
        <ColumnDefinition />
        <ColumnDefinition Width="Auto" Name="column"/>
    </Grid.ColumnDefinitions>

    <TextBox Grid.Column="0" HorizontalAlignment="Stretch" TextWrapping="Wrap" 
             Text="TextBox" VerticalAlignment="Stretch" Background="Aqua"/>

    <Expander Grid.Column="1" Header="Expander" ExpandDirection="Left" 
              HorizontalAlignment="Right" Background="LightBlue" >
        <Expander.Content>
            <Grid>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="5"/>
                    <ColumnDefinition Width="Auto"/>
                </Grid.ColumnDefinitions>

                <TextBlock Text="Some text Some text Some Text" Grid.Column="1"/>
                <GridSplitter Grid.Column="0" Width="5"    
                              ResizeBehavior="PreviousAndCurrent"
                              ResizeDirection="Columns" 
                              HorizontalAlignment="Stretch"/>
            </Grid>
        </Expander.Content>
    </Expander>
</Grid></Window>

找到合适的解决方案。XAML：

<Window x:Class="WpfApplication10.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">

<Window.Resources>
    <BooleanToVisibilityConverter x:Key="BoolToVisConverter"/>
</Window.Resources>

<Grid ShowGridLines="True">
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="*" Name="leftColumn"/>
        <ColumnDefinition Width="Auto"/>
        <ColumnDefinition Width="Auto" Name="rightColumn" />
    </Grid.ColumnDefinitions>

    <TextBox Grid.Column="0"
             HorizontalAlignment="Stretch"
             TextWrapping="Wrap"
             Text="TextBox"
             VerticalAlignment="Stretch"
             Background="Aqua" />

    <Expander Grid.Column="2"
              Name="Expander"
              Header="Expander"
              ExpandDirection="Left"
              Background="LightBlue" 
              Collapsed="Expander_Collapsed" 
              Expanded="Expander_Expanded" >
        <TextBlock Text="Some text Some text Some Text" />
    </Expander>
    <GridSplitter Grid.Column="1"
                  Width="5"
                  ResizeBehavior="PreviousAndNext"
                  ResizeDirection="Columns"
                  VerticalAlignment="Stretch"
                  Height="Auto" 
                  Visibility="{Binding ElementName=Expander, Path=IsExpanded, 
                              Converter={StaticResource BoolToVisConverter}}"/>
</Grid></Window>

后台代码：

    private void Expander_Collapsed(object sender, RoutedEventArgs e)
    {
        leftColumn.Width = new GridLength(1, GridUnitType.Star);
        rightColumn.Width = new GridLength(1, GridUnitType.Auto);
    }

    private void Expander_Expanded(object sender, RoutedEventArgs e)
    {
        rightColumn.Width = new GridLength(1, GridUnitType.Star);
    }