Centering a WPF control

Question

I have a window where I add a new UserControl to (with an image), I simply want to center the control in the middle of the screen (both vertically and horizontally). I can only get the vertical one to work. I'm gonna swap content in the DockPanel from my CodeBehind and want to show this startup screen before I start doing my slideshow UI, this means that the content is set from the CodeBehind.

My Window:

<Window x:Class="GreenWebPlayerWPF.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="512" Width="853" WindowStyle="None" WindowState="Maximized" WindowStartupLocation="CenterScreen">
    <DockPanel Width="Auto" Height="Auto" Name="TransitionContainer" Background="Black" Margin="0" LastChildFill="True"></DockPanel>
</Window>

My UserControl:

<UserControl x:Class="GreenWebPlayerWPF.FrontPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <DockPanel Background="Black">
        <Image Name="image1" Stretch="None" Source="/GreenWebPlayerWPF;component/gw.png" />
    </DockPanel>
</UserControl>

Please note that I'm using maximized/full screen.

Answer 1

Use a Grid:

  <Grid>  
    <Grid.ColumnDefinitions>
      <ColumnDefinition Width="*"/>
      <ColumnDefinition Width="Auto"/>
      <ColumnDefinition Width="*"/>
    </Grid.ColumnDefinitions>
    <Grid.RowDefinitions>
      <RowDefinition Height="*"/>
      <RowDefinition Height="Auto"/>
      <RowDefinition Height="*"/>
    </Grid.RowDefinitions>
    <!-- Replace with your UserControl -->
    <Button Content="Foo" Grid.Column="1" Grid.Row="1"/>
  </Grid>

You can dock it inside your DockPanel (if you must have a DockPanel there) to stretch. And, of course, while the above is all markup, you can just as easily create such a grid from code.