DataGridView每行前面添加序号

private void dataGridView1_RowPostPaint(object sender, DataGridViewRowPostPaintEventArgs e)
        {
            SolidBrush b = new SolidBrush(this.dataGridView1.RowHeadersDefaultCellStyle.ForeColor);
            e.Graphics.DrawString((e.RowIndex + 1).ToString(System.Globalization.CultureInfo.CurrentUICulture), this.dataGridView1.DefaultCellStyle.Font,b,e.RowBounds.Location.X + 20,e.RowBounds.Location.Y + 4);
        }