panel 绑定鼠标滚轮事件

 void formsample_mousewheel(object sender, MouseEventArgs e)
         {
             //获取光标位置
             Point mousepoint = new Point(e.X, e.Y);
             //换算成相对本窗体的位置
             mousepoint.Offset(this.Location.X, this.Location.Y);
             //判断是否在panel内
             if (pl_message.RectangleToScreen(pl_message.DisplayRectangle).Contains(mousepoint))
             {
                 //滚动
                 pl_message.AutoScrollPosition = new Point(, pl_message.VerticalScroll.Value - e.Delta);
             }
         }

  this.MouseWheel += formsample_mousewheel;