Show the effect of each value of the Dock property by manipulating two Rectangle elements.

   
  

<Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      x:Class="WpfApplication1.Page1"
      WindowTitle="Docking Sample">
  <DockPanel Background="White">
    <StackPanel Orientation="Horizontal" DockPanel.Dock="Top" Margin="0,0,0,10">
      <Button Click="OnClick1" Background="LightCoral">Dock = "Left"</Button>
      <Button Click="OnClick2" Background="LightCoral">Dock = "Right"</Button>
      <Button Click="OnClick3" Background="LightCoral">Dock = "Top"</Button>
      <Button Click="OnClick4" Background="LightCoral">Dock = "Bottom"</Button>
      <Button Click="OnClick5" Background="LightSkyBlue" Foreground="White">Dock = "Left"</Button>
      <Button Click="OnClick6" Background="LightSkyBlue" Foreground="White">Dock = "Right"</Button>
      <Button Click="OnClick7" Background="LightSkyBlue" Foreground="White">Dock = "Top"</Button>
      <Button Click="OnClick8" Background="LightSkyBlue" Foreground="White">Dock = "Bottom"</Button>
      <Button Click="OnClick9" Background="White">LastChildDock="True"</Button>
      <Button Click="OnClick10" Background="White">LastChildDock="False"</Button>
    </StackPanel>

    <Border Background="LightGoldenRodYellow" BorderBrush="Black" BorderThickness="1">
      <DockPanel Name="AnotherDockPanel">
        <Rectangle Name="rect1" MinWidth="200" MinHeight="200" Stroke="Black" Fill="LightCoral" />
        <Rectangle Name="rect2" MinWidth="200" MinHeight="200" Stroke="Black" Fill="LightSkyBlue" />
      </DockPanel>
    </Border>
  </DockPanel>
</Page>

//File:Window.xaml.cs
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Documents;
using System.Windows.Navigation;

namespace WpfApplication1
{
    public partial class Page1 : Page
    {
        public void OnClick1(object sender, RoutedEventArgs e)
        {
            DockPanel.SetDock(rect1, Dock.Left);
        }
       
        public void OnClick2(object sender, RoutedEventArgs e)
        {
            DockPanel.SetDock(rect1, Dock.Right);
        }

        public void OnClick3(object sender, RoutedEventArgs e)
        {
            DockPanel.SetDock(rect1, Dock.Top);
        }

        public void OnClick4(object sender, RoutedEventArgs e)
        {
            DockPanel.SetDock(rect1, Dock.Bottom);
        }

        public void OnClick5(object sender, RoutedEventArgs e)
        {
            DockPanel.SetDock(rect2, Dock.Left);
        }

        public void OnClick6(object sender, RoutedEventArgs e)
        {
            DockPanel.SetDock(rect2, Dock.Right);
        }

        public void OnClick7(object sender, RoutedEventArgs e)
        {
            DockPanel.SetDock(rect2, Dock.Top);
        }

        public void OnClick8(object sender, RoutedEventArgs e)
        {
            DockPanel.SetDock(rect2, Dock.Bottom);
        }

        public void OnClick9(object sender, RoutedEventArgs e)
        {
            AnotherDockPanel.LastChildFill = true;
        }

        public void OnClick10(object sender, RoutedEventArgs e)
        {
            AnotherDockPanel.LastChildFill = false;
        }
    }
}