How can I vertically align a TextBox inside a StackPanel?

Question

In the following XAML, the word "Test" centers horizontally but not vertically.

How can I get it to center vertically?

<Window x:Class="TestVerticalAlign2343.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        WindowStartupLocation="CenterScreen"
    Title="Window1" Height="768" Width="1024">
    <DockPanel LastChildFill="True">
        <Slider x:Name="TheSlider"
                DockPanel.Dock="Left"
                Orientation="Vertical"
                HorizontalAlignment="Center"
                HorizontalContentAlignment="Center"
                Minimum="0"
                Maximum="10"
                Cursor="Hand"
                Value="{Binding CurrentSliderValue}"
                IsDirectionReversed="True"
                IsSnapToTickEnabled="True"
                Margin="10 10 0 10"/>
        <Border DockPanel.Dock="Right" Background="Beige"
                Padding="10"
                Margin="10"
                CornerRadius="5">
            <StackPanel Height="700">
                <TextBlock
                    Text="Test"
                    HorizontalAlignment="Center"
                    VerticalAlignment="Center"
                    FontSize="200" x:Name="TheNumber"/>

            </StackPanel>
        </Border>
    </DockPanel>
</Window>

Answer 1

Inside the StackPanel that surrounds the TextBlock, check out VerticalContentAlignment.

Answer 2

Seems I asked this question 10 months ago, I got the above scenario to work by replacing the StackPanel with DockPanel LastChildFill=True like this:

<DockPanel LastChildFill="True">
    <TextBlock
        DockPanel.Dock="Top"
        Text="Test"
        HorizontalAlignment="Center"
        VerticalAlignment="Center"
        FontSize="200" x:Name="TheNumber"/>
</DockPanel>

Answer 3

A stackpanel, no matter how you stretch it, will collapse around the children. you can't make it grow more than that. Basically, that "Height=700" is not helping you.

So either set VerticalAlignment on the StackPanel to "center" so that the stackpanel goes into the center of the dockpanel...or remove the stackpanel altogether and set VerticalAlignment="Center" on the TextBlock.