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>
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.