private void dataGridView1_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)//绘制单元格事件

        {

            // 对第1列相同单元格进行合并     

            if(e.ColumnIndex == 2 && e.RowIndex != -1 || e.ColumnIndex == 3 && e.RowIndex != -1 || e.ColumnIndex == 4 && e.RowIndex != -1) {

                Brush datagridBrush = new SolidBrush(dataGridView1.GridColor);

                SolidBrush groupLineBrush = new SolidBrush(e.CellStyle.BackColor);

                using(Pen datagridLinePen = new Pen(datagridBrush)) {

                    // 清除单元格

                    e.Graphics.FillRectangle(groupLineBrush, e.CellBounds);

                    if(e.RowIndex < dataGridView1.Rows.Count - 1 && dataGridView1.Rows[e.RowIndex + 1].Cells[e.ColumnIndex].Value != null && dataGridView1.Rows[e.RowIndex + 1].Cells[e.ColumnIndex].Value.ToString() != e.Value.ToString()) {

                        //绘制底边线

                        e.Graphics.DrawLine(datagridLinePen, e.CellBounds.Left, e.CellBounds.Bottom - 1, e.CellBounds.Right, e.CellBounds.Bottom - 1);

                        // 画右边线

                        e.Graphics.DrawLine(datagridLinePen, e.CellBounds.Right - 1, e.CellBounds.Top, e.CellBounds.Right - 1, e.CellBounds.Bottom);

                    }