在DataTemplate Stretch中创建最后一个TextBox

I have an ItemsControl:

我有一个ItemsControl：

<Border Grid.Row="1" Margin="20" BorderBrush="AliceBlue" BorderThickness="1" VerticalAlignment="Stretch" HorizontalAlignment="Stretch">
   <ItemsControl Margin="10" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" ItemsSource="{Binding SelectedEventHistoryEntryCollection}" ItemTemplateSelector="{StaticResource computerEventHistoryDataTemplateSelector}"/>
</Border>
<