Halting event routing with Handled

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<Window x:Class="WpfApplication1.HaltingEvents"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Halting Events" Height="300" Width="300">
  <Grid HorizontalAlignment="Center" VerticalAlignment="Center">
    <Button PreviewMouseDown="PreviewMouseDownButton"
    MouseDown="MouseDownButton">

      <Grid PreviewMouseDown="PreviewMouseDownGrid"
            MouseDown="MouseDownGrid">
        <Grid.ColumnDefinitions>
          <ColumnDefinition />
          <ColumnDefinition />
        </Grid.ColumnDefinitions>

        <Canvas PreviewMouseDown="PreviewMouseDownCanvas"
                MouseDown="ButtonDownCanvas"
                Width="20" Height="18" VerticalAlignment="Center">

          <Ellipse PreviewMouseDown="PreviewMouseDownEllipse"
                   MouseDown="MouseDownEllipse"
                   x:Name="myEllipse"
                   Canvas.Left="1" Canvas.Top="1" Width="16" Height="16"
                   Fill="Yellow" Stroke="Black" />

          <Ellipse Canvas.Left="4.5" Canvas.Top="5" Width="2.5" Height="3"
                   Fill="Black" />
          <Ellipse Canvas.Left="11" Canvas.Top="5" Width="2.5" Height="3"
                   Fill="Black" />
          <Path Data="M 5,10 A 3,3 0 0 0 13,10" Stroke="Black" />
        </Canvas>

        <TextBlock Grid.Column="1">Click!</TextBlock>
      </Grid>
    </Button>
  </Grid>
</Window>



//File:Window.xaml.cs

using System;
using System.Windows;
using System.Diagnostics;

namespace WpfApplication1
{
    public partial class HaltingEvents : System.Windows.Window
    {

        public HaltingEvents()
        {
            InitializeComponent();
        }
        void ButtonDownCanvas(object sender, RoutedEventArgs e)
        {
            Debug.WriteLine("ButtonDownCanvas");
            e.Handled = true;
        }
        void PreviewMouseDownButton(object sender, RoutedEventArgs e)
        { Debug.WriteLine("PreviewMouseDownButton"); }

        void MouseDownButton(object sender, RoutedEventArgs e)
        { Debug.WriteLine("MouseDownButton"); }


        void PreviewMouseDownGrid(
          object sender, RoutedEventArgs e)
        { Debug.WriteLine("PreviewMouseDownGrid"); }

        void MouseDownGrid(object sender, RoutedEventArgs e)
        { Debug.WriteLine("MouseDownGrid"); }


        void PreviewMouseDownCanvas(object sender, RoutedEventArgs e)
        { Debug.WriteLine("PreviewMouseDownCanvas"); }


        void PreviewMouseDownEllipse(object sender, RoutedEventArgs e)
        { Debug.WriteLine("PreviewMouseDownEllipse"); }

        void MouseDownEllipse(object sender, RoutedEventArgs e)
        { Debug.WriteLine("MouseDownEllipse"); }
    }
}