XAML树视图垂直展开

我希望下面的TreeView扩展以填充它所包含的当前行,但是,我不知道这是如何完成的。它只是扩展以适应树项目。这可以做到吗?如果可以,如何做到?

谢谢

<Window x:Class="WorkoutUI.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Name="Window" Height="350" Width="525">
    <Grid Name="Root_Grid">
        <Grid.RowDefinitions>
            <RowDefinition Height="10" />
            <RowDefinition Height="*" Name="Root_Grid_Row_2" />
            <RowDefinition Height="10" />            
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="5" />
            <ColumnDefinition Width="150" />
            <ColumnDefinition Width="*" />
            <ColumnDefinition Width="5" />
        </Grid.ColumnDefinitions>

        <TreeView Grid.Column="1" Grid.Row="1" VerticalAlignment="Top" VerticalContentAlignment="Stretch" Width="{Binding Width, ElementName=Root_Grid, Mode=Default}">
            <TreeViewItem Header="Workouts" IsExpanded="True">
                <TreeViewItem Header="Workout1" />
                <TreeViewItem Header="Workout2" />
                <TreeViewItem Header="Workout3" IsExpanded="True">
                    <TreeViewItem Header="WorkoutSub1" />
                    <TreeViewItem Header="WorkoutSub2" />
                    <TreeViewItem Header="WorkoutSub3" />
                </TreeViewItem>    
                <TreeViewItem Header="Workout4" />
                <TreeViewItem Header="Workout5" />
                <TreeViewItem Header="Workout6" />                
            </TreeViewItem>            
        </TreeView>
    </Grid>
</Window>