void DrawCenterLine(ControlGraphicsInfoArgs info)
        {
            AppearanceObject obj = new AppearanceObject();

            obj.BackColor    = Color.Gray;
            obj.BackColor2   = Color.Black;
            obj.GradientMode = System.Drawing.Drawing2D.LinearGradientMode.Vertical;
            obj.FillRectangle(info.Cache, calc.CenterBounds);
            obj.Dispose();
        }