AvalonPaint, My First WPF Application

    After playing for a while with the January CTP release of Windows Presentation Foundation, formerly known as Avalon, I write a simple application with which you can draw the lines continuously using mouse, the  XAML code and corresponding C# code dealing with the interactive logic is listed as follows:
DrawingWindow.xaml:

<Window x:Class="AvalonPaint.DrawingWindow"
    xmlns="http://schemas.microsoft.com/winfx/avalon/2005"
    xmlns:x="http://schemas.microsoft.com/winfx/xaml/2005"
    Title="AvalonPaint"
    Loaded="DrawingWindow_Loaded" Height="400" Width="600">
  <Window.Resources>
    <DrawingBrush x:Key="backgroundResource"
                              Viewport="0,0,10,10" ViewportUnits="Absolute" TileMode="Tile">
      <DrawingBrush.Drawing>
        <DrawingGroup>
          <DrawingGroup.Children>
            <GeometryDrawing Brush="White">
              <GeometryDrawing.Geometry>
                <RectangleGeometry Rect="0,0,1,1" />
              </GeometryDrawing.Geometry>
            </GeometryDrawing>
            <GeometryDrawing Brush="#AAE6E8F6"
              Geometry="M 0,0 L 0,1 0.1,1 0.1,0.1 1,0.1 1,0 Z" />
          </DrawingGroup.Children>
        </DrawingGroup>
      </DrawingBrush.Drawing>
    </DrawingBrush>
  </Window.Resources>
    <Grid>
      <Grid.ColumnDefinitions>
        <ColumnDefinition />
      </Grid.ColumnDefinitions>
      <Grid.RowDefinitions>
        <RowDefinition />
      </Grid.RowDefinitions>
      <Canvas Name="drawingBoard" Grid.Column="0" Grid.Row="0" Background="{StaticResource backgroundResource}"/>
      <StackPanel Name="capturePanel" Background="Transparent"/>
    </Grid>
</Window>

DrawingWindow.xaml.cs:

using System;
using System.Windows;
using System.Windows.Input;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;


namespace AvalonPaint
{
    /// <summary>
    /// Interaction logic for DrawingWindow.xaml
    /// </summary>

    public partial class DrawingWindow : Window
    {
        private Boolean isDrawing = false;
        private Point startPoint;
        public DrawingWindow()
        {
            InitializeComponent();
        }

        private void DrawingWindow_Loaded(Object sender, RoutedEventArgs e)
        {
            capturePanel.MouseDown += capturePanel_MouseDown;
            capturePanel.MouseMove += capturePanel_MouseMove;
            capturePanel.MouseUp += capturePanel_MouseUp;
        }

        private void capturePanel_MouseDown(Object sender, MouseEventArgs e)
        {
            isDrawing = true;
            startPoint = e.GetPosition(this);
        }

        private void capturePanel_MouseMove(Object sender, MouseEventArgs e)
        {
            if (isDrawing && e.LeftButton == MouseButtonState.Pressed)
            {
                Point endPoint = e.GetPosition(this);
                DrawLine(startPoint, endPoint, drawingBoard);
                startPoint = endPoint;
            }
        }

        private void capturePanel_MouseUp(Object sender, MouseEventArgs e)
        {
            startPoint = e.GetPosition(this);

            //Disable mouse capture for the current Window element.
            Mouse.Capture(this, CaptureMode.None);
            isDrawing = false;
        }

        // Private helper method responsible for drawing lines in the surface of Canvas element.
        private void DrawLine(Point from, Point to, Canvas targetCanvas)
        {
            Line line = new Line();
            line.StrokeEndLineCap = PenLineCap.Round;
            line.StrokeStartLineCap = PenLineCap.Round;
            line.Stroke = Brushes.Red;
            line.StrokeThickness = 3.0;
            line.X1 = from.X;
            line.Y1 = from.Y;
            line.X2 = to.X;
            line.Y2 = to.Y;
            Canvas.SetLeft(targetCanvas, from.X);
            Canvas.SetTop(targetCanvas, from.Y);
            targetCanvas.Children.Add(line);
        }
    }
}

    One caveat here is that it seems the Canvas element cannot capture any mouse event, for instance MouseDown, MouseUp and MouseMove events, after digging into this problem for a while, I find a workaround by overlapping a transparent StackPanel element named capturePanel on top of the Canvas  element, and hook up mouse event handlers with this capturePanel's corresponding mouse events, I can actually capture the mouse events for the Canvas element, and then draw the line in it.
    It's simple but quite interesting, please enjoy it!