控件拖拽

        private bool dragging;
        Point mousePoint;
        TextBlock mouseCtrl = null;
        Rectangle shadow = new Rectangle();
        public MainWindow()
        {
            InitializeComponent();
            c.Children.Insert(0, shadow);
        }

        private void button1_MouseDown(object sender, MouseButtonEventArgs e)
        {

            if (e.LeftButton == MouseButtonState.Pressed)
            {
                dragging = true;
                mousePoint = e.GetPosition(this.c);
                mouseCtrl = (TextBlock)e.Source; 
                mouseCtrl.Visibility = Visibility.Collapsed;
                shadow.Width = mouseCtrl.Width;
                shadow.Height = mouseCtrl.Height;
                shadow.Fill = Brushes.Red;
                Canvas.SetLeft(shadow, Canvas.GetLeft(mouseCtrl));
                Canvas.SetTop(shadow, Canvas.GetTop(mouseCtrl));
                shadow.Visibility = Visibility.Visible;
                c.CaptureMouse();
            }   
        }

        private void button1_MouseMove(object sender, MouseEventArgs e)
        {
            if (dragging)
            {
                if (e.LeftButton == MouseButtonState.Pressed)
                {
                    Point theMousePoint = e.GetPosition(this.c);
                    Console.WriteLine("Move: left:" + Canvas.GetLeft(mouseCtrl) + "    top:" + Canvas.GetTop(mouseCtrl));
                    Canvas.SetLeft(shadow, theMousePoint.X - (mousePoint.X - Canvas.GetLeft(shadow)));
                    Canvas.SetTop(shadow, theMousePoint.Y - (mousePoint.Y - Canvas.GetTop(shadow)));//简单的计算，只移动shadow   
                    mousePoint = theMousePoint;
                }
            }    
        }

        private void button1_MouseUp(object sender, MouseButtonEventArgs e)
        {

            dragging = false;
            Mouse.Capture(null);
            shadow.Visibility = Visibility.Hidden;
            mouseCtrl.Visibility = Visibility.Visible;
            Canvas.SetLeft(mouseCtrl, Canvas.GetLeft(shadow));
            Canvas.SetTop(mouseCtrl, Canvas.GetTop(shadow));
        }