void drawhost_MouseLeftButtonDown(object sender, System.Windows.Input.MouseButtonEventArgs e)
{
if (points == null)
{
drawhost.MouseMove += new System.Windows.Input.MouseEventHandler(drawhost_MouseMove);
drawhost.MouseLeftButtonUp += new System.Windows.Input.MouseButtonEventHandler(drawhost_MouseLeftButtonUp);
points = new List<Point>();
points.Add(e.GetPosition(drawhost));
points.Add(e.GetPosition(drawhost));
Brush br = Brushes.LightGreen;
area = new AreaVisual(pen);
drawhost.Add(area);
area.Points = points;
points_toget = points;
area.Redraw();
}
}