Drag Move UI Element inside a Canvas

        private Point m_StartPoint;
        private double m_OriginalLeft;
        private double m_OriginalTop;
        private Boolean m_IsDown;
        private UIElement m_OriginalElement;
        private Boolean m_IsDragging;

        private void MyCanvas_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            if (MyCanvas == e.Source || !AllowMove) return;
            m_IsDown = true;
            m_StartPoint = e.GetPosition(MyCanvas);
            m_OriginalElement = e.Source as UIElement;
            MyCanvas.CaptureMouse();
            e.Handled = true;
        }

        private void MyCanvas_PreviewMouseMove(object sender, System.Windows.Input.MouseEventArgs e)
        {
            if (m_IsDown)
            {
                if (!m_IsDragging && Math.Abs(e.GetPosition(MyCanvas).X - m_StartPoint.X) > SystemParameters.MinimumHorizontalDragDistance && Math.Abs(e.GetPosition(MyCanvas).Y - m_StartPoint.Y) > SystemParameters.MinimumVerticalDragDistance)
                {
                    DragStarted();
                }
                if (m_IsDragging)
                {
                    DragMoved();
                }
            }
        }


        private void MyCanvas_PreviewMouseLeftButtonUp(object sender, System.Windows.Input.MouseButtonEventArgs e)
        {
            if (m_IsDown)
            {
                DragFinished(false);
                e.Handled = true;
            }
        }

        private void DragFinished(bool p)
        {
            System.Windows.Input.Mouse.Capture(null);
            m_IsDragging = false;
            m_IsDown = false;
        }
        private void DragMoved()
        {
            Point currentPosition = System.Windows.Input.Mouse.GetPosition(MyCanvas);
            double elementLeft = (currentPosition.X - m_StartPoint.X) + m_OriginalLeft;
            double elementTop = (currentPosition.Y - m_StartPoint.Y) + m_OriginalTop;
            Canvas.SetLeft(m_OriginalElement, elementLeft);
            Canvas.SetTop(m_OriginalElement, elementTop);            
        }

        private void DragStarted()
        {
            m_IsDragging = true;
            m_OriginalLeft = Canvas.GetLeft(m_OriginalElement);
            m_OriginalTop = Canvas.GetTop(m_OriginalElement);
            
        }