datagridview 单元格合并

void dgResult_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)
        {
            if (e.ColumnIndex == 0 && e.RowIndex != -1)
            {
                using
                    (
                    Brush gridBrush = new SolidBrush(this.dgResult.GridColor),
                    backColorBrush = new SolidBrush(e.CellStyle.BackColor)
                    )
                {
                    using (Pen gridLinePen = new Pen(gridBrush))
                    {
                        e.Graphics.FillRectangle(backColorBrush, e.CellBounds);
                        if (e.RowIndex < dgResult.Rows.Count - 1 &&
                        dgResult.Rows[e.RowIndex + 1].Cells[e.ColumnIndex].Value.ToString() !=
                        e.Value.ToString())
                            e.Graphics.DrawLine(gridLinePen, e.CellBounds.Left,
                            e.CellBounds.Bottom - 1, e.CellBounds.Right - 1,
                            e.CellBounds.Bottom - 1);
                        e.Graphics.DrawLine(gridLinePen, e.CellBounds.Right - 1,
                            e.CellBounds.Top, e.CellBounds.Right - 1,
                            e.CellBounds.Bottom);
                        if (e.Value != null)
                        {
                            if (e.RowIndex > 0 &&
                            dgResult.Rows[e.RowIndex - 1].Cells[e.ColumnIndex].Value.ToString() ==
                            e.Value.ToString())
                            { }
                            else
                            {
                                e.Graphics.DrawString((String)e.Value, e.CellStyle.Font,
                                    Brushes.Black, e.CellBounds.X + 2,
                                    e.CellBounds.Y + 5, StringFormat.GenericDefault);
                            }
                        }
                        e.Handled = true;
                    }
                }
            }
        }