/// <summary>
        /// 显示行号
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void DataGridViewEx_RowPostPaint(object sender, DataGridViewRowPostPaintEventArgs e)
        {
            if (showRowHeaderNumbers)
            {
                string title = (e.RowIndex + 1).ToString();
                Brush bru = Brushes.Black;
                e.Graphics.DrawString(title, DefaultCellStyle.Font,
                    bru, e.RowBounds.Location.X + RowHeadersWidth / 2 - 4, e.RowBounds.Location.Y + 4);
            }
        }