datagridview合并单元格

可以使用以下代码实现DataGridView的单元格合并功能：

private void DataGridView_CellPaintingMergeCell(object sender, DataGridViewCellPaintingEventArgs e, int columnIndex)
{
    if (e.RowIndex < 0 || e.ColumnIndex < 0)
    {
        return;
    }

    DataGridView dataGridView = sender as DataGridView;
    if (dataGridView == null)
    {
        return;
    }

    DataGridViewCell cell = dataGridView[columnIndex, e.RowIndex];
    if (cell == null)
    {
        return;
    }

    int rowspan = 1;
    for (int i = e.RowIndex + 1; i < dataGridView.Rows.Count; i++)
    {
        DataGridViewCell nextCell = dataGridView[columnIndex, i];
        if (nextCell == null)
        {
            break;
        }

        if (cell.Value == nextCell.Value)
        {
            rowspan++;
            dataGridView[columnIndex, i].Visible = false;
        }
        else
        {
            break;
        }
    }

    if (rowspan > 1)
    {
        Rectangle rect = new Rectangle(e.CellBounds.Left, e.CellBounds.Top, e.CellBounds.Width, e.CellBounds.Height * rowspan);
        e.Graphics.FillRectangle(new SolidBrush(e.CellStyle.BackColor), rect);
        e.Graphics.DrawRectangle(new Pen(dataGridView.GridColor), rect);
        e.Graphics.DrawString(cell.Value.ToString(), e.CellStyle.Font, new SolidBrush(e.CellStyle.ForeColor), rect, new StringFormat() { Alignment = StringAlignment.Center, LineAlignment = StringAlignment.Center });
        e.Handled = true;
    }
}

在DataGridView的CellPainting事件中调用该方法即可实现单元格合并。例如：

private void dataGridView1_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)
{
    DataGridView_CellPaintingMergeCell(sender, e, 2);
}

其中，第三个参数2表示要合并的列的索引。如果需要合并多列，可以在CellPainting事件中多次调用该方法，分别传入不同的列索引即可。