Datagridview合并单元格

private void dataGridView1_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)
        {
           
            if (dataGridView1.Rows.Count > 0)
            {

                if (dataGridView1.Rows[0].Cells[0].Value.ToString().Trim() != string.Empty)
                {
                    try
                    {
                        for (int i = 0; i < dataGridView1.Rows.Count; i++)
                        {
                            #region MyRegion
                            if (dataGridView1.Columns[i].Index == e.ColumnIndex && e.RowIndex >= 0)
                            {
                                using (
                                    Brush gridBrush = new SolidBrush(dataGridView1.GridColor),
                                    backColorBrush = new SolidBrush(e.CellStyle.BackColor))
                                    {
                                        using (Pen gridLinePen = new Pen(gridBrush))
                                        {
                                            // 擦除原单元格背景
                                            e.Graphics.FillRectangle(backColorBrush, e.CellBounds);

                                            if (e.RowIndex != dataGridView1.RowCount - 1)
                                            {
                                                if (e.Value.ToString() != dataGridView1.Rows[e.RowIndex + 1].Cells[e.ColumnIndex].Value.ToString())
                                                {
                                                    e.Graphics.DrawLine(gridLinePen, e.CellBounds.Left, e.CellBounds.Bottom - 1,
                                                    e.CellBounds.Right - 1, e.CellBounds.Bottom - 1);//下边缘的线 
                                                }
                                            }
                                            else
                                            {
                                                e.Graphics.DrawLine(gridLinePen, e.CellBounds.Left, e.CellBounds.Bottom - 1,
                                                    e.CellBounds.Right - 1, e.CellBounds.Bottom - 1);//下边缘的线                       
                                            }

                                            //右侧的线
                                            e.Graphics.DrawLine(gridLinePen, e.CellBounds.Right - 1, //x1,y1,x2,y2
                                                e.CellBounds.Top, e.CellBounds.Right - 1,
                                                e.CellBounds.Bottom - 1);

                                            #region MyRegion
                                            if (e.RowIndex == 0)
                                            {
                                                //绘制第一列的值
                                                if (e.Value != null)
                                                {

                                                    e.Graphics.DrawString((String)e.Value, e.CellStyle.Font,
                                                        Brushes.Crimson,
                                                        e.CellBounds.X + (e.CellBounds.Width - e.Graphics.MeasureString(e.Value.ToString().Trim(), e.CellStyle.Font).Width) / 2,
                                                        e.CellBounds.Y + 2, StringFormat.GenericDefault);
                                                }
                                            }
                                            else
                                            {
                                                if (e.Value.ToString() != dataGridView1.Rows[e.RowIndex - 1].Cells[e.ColumnIndex].Value.ToString())
                                                {
                                                    //绘制值
                                                    if (string.IsNullOrEmpty(e.Value.ToString().Trim()).Equals(false))
                                                    {
                                                        e.Graphics.DrawString((String)e.Value, e.CellStyle.Font,
                                                            Brushes.Crimson, e.CellBounds.X + (e.CellBounds.Width - e.Graphics.MeasureString(e.Value.ToString().Trim(), e.CellStyle.Font).Width) / 2,
                                                            e.CellBounds.Y + 2, StringFormat.GenericDefault);
                                                    }
                                                }
                                            }
                                            #endregion

                                            e.Handled = true;
                                        }
                                    }
                            }
                            #endregion
                        }

                        
                    }
                    catch { }
                }
            }
        }

        /// <summary>
        /// 添加一个表格
        /// </summary>
        public void addDatatable()
        {

            DataColumn dc = new DataColumn("ID");
            dt.Columns.Add(dc);
            dc = new DataColumn("name");
            dt.Columns.Add(dc);
            dc = new DataColumn("age");
            dt.Columns.Add(dc);
            dc = new DataColumn("sex");
            dt.Columns.Add(dc);

            dt.Rows.Add(2, "上海", "5000", "7000");
            dt.Rows.Add(2, "北京", "3000", "5600");
            dt.Rows.Add(3, "纽约", "6000", "8600");
            dt.Rows.Add(3, "华盛顿", "8000", "9000");
            dt.Rows.Add(4, "伦敦", "7000", "8800");
        }