在水平列表框中,如何将项与顶部对齐?

在水平列表框中,如何将项与顶部对齐?

我已经没有办法把垂直线放在哪里了。

<Window.Resources>
    <DataTemplate DataType="{x:Type l:MyType}">
        <Grid VerticalAlignment="Top">
            <TextBlock VerticalAlignment="Top" Text="{Binding MyValue}" Background="Yellow"/>
        </Grid>
    </DataTemplate>    
</Window.Resources>   

<Grid>
    <ListBox Name="listBox" ItemsSource="{Binding}"  VerticalAlignment="Top" >

        <ListBox.ItemsPanel>
            <ItemsPanelTemplate>
                <StackPanel Orientation="Horizontal" VerticalAlignment="Top"/>
            </ItemsPanelTemplate>
        </ListBox.ItemsPanel>

        <ListBox.ItemTemplate>
            <DataTemplate>
                <ListBoxItem Content="{Binding}" VerticalAlignment="Top" VerticalContentAlignment="Top"/>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>
</Grid>

using System.Windows;

namespace WpfApplication5 {
    public partial class Window1 :Window {
        public Window1() {
            InitializeComponent();
            this.listBox.ItemsSource = new MyType[] {
                new MyType{ MyValue = "Tall\nItem" },
                new MyType{ MyValue = "I want this aligned to the top" } };
        }
    }

    public class MyType {
        public string MyValue { get; set; }
    }
}