ASP.net下實現合并單元格相對簡單，很大程度上是因為基於HTML；Winform下的DataGridView實現比較繁瑣，目前看似只有重繪這條路；如果嫌累可以使用Developer Express .NET的全套解決方案；

[轉載]二维表头的实现，來源不明

int top = 0;
        int left = 0;
        int height = 0;
        int width1 = 0;
        private void dataGridView1_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)
        {
            #region 重绘datagridview表头
            DataGridView dgv = (DataGridView)(sender);
            if (e.RowIndex == -1 && (e.ColumnIndex == 3 || e.ColumnIndex == 4))
            {

//e.CellStyle.Font = new Font(dataGridView1.DefaultCellStyle.Font, FontStyle.Bold);
                //e.CellStyle.WrapMode = DataGridViewTriState.True;
                if (e.ColumnIndex == 3)
                {
                    top = e.CellBounds.Top;
                    left = e.CellBounds.Left;
                    height = e.CellBounds.Height;
                    width1 = e.CellBounds.Width;
                }

int width2 = this.dataGridView1.Columns[4].Width;

Rectangle rect = new Rectangle(left, top, width1 + width2, e.CellBounds.Height);
                using (Brush backColorBrush = new SolidBrush(e.CellStyle.BackColor))
                {
                    //抹去原来的cell背景
                    e.Graphics.FillRectangle(backColorBrush, rect);
                }

using (Pen gridLinePen = new Pen(dgv.GridColor))
                {
                    e.Graphics.DrawLine(gridLinePen, left, top, left + width1 + width2, top);
                    e.Graphics.DrawLine(gridLinePen, left, top + height / 2, left + width1 + width2, top + height /

2);
                    e.Graphics.DrawLine(gridLinePen, left + width1, top + height / 2, left + width1, top + height);

//计算绘制字符串的位置
                    string columnValue = "Year";
                    SizeF sf = e.Graphics.MeasureString(columnValue, e.CellStyle.Font);
                    float lstr = (width1 + width2 - sf.Width) / 2;
                    float rstr = (height / 2 - sf.Height) / 2;
                    //画出文本框

if (columnValue != "")
                    {
                        e.Graphics.DrawString(columnValue, e.CellStyle.Font,
                                                   new SolidBrush(e.CellStyle.ForeColor),
                                                     left + lstr,
                                                     top + rstr,
                                                     StringFormat.GenericDefault);
                    }

//计算绘制字符串的位置
                    columnValue = "局网台资产额";
                    sf = e.Graphics.MeasureString(columnValue, e.CellStyle.Font);
                    lstr = (width1 - sf.Width) / 2;
                    rstr = (height / 2 - sf.Height) / 2;
                    //画出文本框

if (columnValue != "")
                    {
                        e.Graphics.DrawString(columnValue, e.CellStyle.Font,
                                                   new SolidBrush(e.CellStyle.ForeColor),
                                                     left + lstr,
                                                     top + height / 2 + rstr,
                                                     StringFormat.GenericDefault);
                    }

//计算绘制字符串的位置
                    columnValue = "网络资产额";
                    sf = e.Graphics.MeasureString(columnValue, e.CellStyle.Font);
                    lstr = (width2 - sf.Width) / 2;
                    rstr = (height / 2 - sf.Height) / 2;
                    //画出文本框

if (columnValue != "")
                    {
                        e.Graphics.DrawString(columnValue, e.CellStyle.Font,
                                                   new SolidBrush(e.CellStyle.ForeColor),
                                                     left + width1 + lstr,
                                                     top + height / 2 + rstr,
                                                     StringFormat.GenericDefault);
                    }

}
                e.Handled = true;

}
            #endregion
        }

http://www.cnblogs.com/liuke209/archive/2006/07/29/463023.html

using System;
using System.Collections.Generic;
using System.Text;

using System.Windows.Forms;
using System.Collections;
using System.Drawing;

namespace OPSS.Logic.Checks
{
    /// <summary>
    /// 对DataGridView进行合并操作的类
    /// </summary>
    public class DGVOper
    {
                
        private static SortedList rowSpan = new SortedList();//取得需要重新绘制的单元格
        private static string rowValue = "";//重新绘制的文本框内容
       
        #region  单元格绘制
        /// <summary>
        ///
        /// DataGridView合并单元格(横向)
        /// </summary>
        /// <param name="dgv">绘制的DataGridview </param>
        /// <param name="cellArgs">绘制单元格的参数（DataGridview的CellPainting事件中参数）</param>
        /// <param name="minColIndex">起始单元格在DataGridView中的索引号</param>
        /// <param name="maxColIndex">结束单元格在DataGridView中的索引号</param>
        public static void MerageRowSpan(DataGridView dgv, DataGridViewCellPaintingEventArgs cellArgs, int minColIndex, int maxColIndex)
        {
            if (cellArgs.ColumnIndex < minColIndex || cellArgs.ColumnIndex > maxColIndex) return;

Rectangle rect=new Rectangle();
            using (Brush gridBrush = new SolidBrush(dgv.GridColor),
                backColorBrush = new SolidBrush(cellArgs.CellStyle.BackColor))
            {
                //抹去原来的cell背景
                cellArgs.Graphics.FillRectangle(backColorBrush, cellArgs.CellBounds);
            }
            cellArgs.Handled = true;

if (rowSpan[cellArgs.ColumnIndex] == null)
            {
                //首先判断当前单元格是不是需要重绘的单元格
                //保留此单元格的信息，并抹去此单元格的背景
                rect.X = cellArgs.CellBounds.X;
                rect.Y = cellArgs.CellBounds.Y;
                rect.Width = cellArgs.CellBounds.Width;
                rect.Height = cellArgs.CellBounds.Height;
               
                rowValue += cellArgs.Value.ToString();
                rowSpan.Add(cellArgs.ColumnIndex, rect);
                if (cellArgs.ColumnIndex != maxColIndex)
                    return;
                MeragePrint(dgv, cellArgs, minColIndex, maxColIndex);
            }
            else
            {
                IsPostMerage(dgv, cellArgs, minColIndex, maxColIndex);
            }
        }

/// <summary>
        /// 不是初次单元格绘制
        /// </summary>
        /// <param name="dgv"></param>
        /// <param name="cellArgs"></param>
        /// <param name="minColIndex"></param>
        /// <param name="maxColIndex"></param>
        public static void IsPostMerage(DataGridView dgv, DataGridViewCellPaintingEventArgs cellArgs, int minColIndex, int maxColIndex)
        {
            //比较单元是否有变化
            Rectangle rectArgs = (Rectangle)rowSpan[cellArgs.ColumnIndex];
            if (rectArgs.X != cellArgs.CellBounds.X || rectArgs.Y != cellArgs.CellBounds.Y
                || rectArgs.Width != cellArgs.CellBounds.Width || rectArgs.Height != cellArgs.CellBounds.Height)
            {
                rectArgs.X = cellArgs.CellBounds.X;
                rectArgs.Y = cellArgs.CellBounds.Y;
                rectArgs.Width = cellArgs.CellBounds.Width;
                rectArgs.Height = cellArgs.CellBounds.Height;
                rowSpan[cellArgs.ColumnIndex] = rectArgs;
            }
            MeragePrint(dgv,cellArgs,minColIndex,maxColIndex);
           
        }

//画制单元格
        private static void MeragePrint(DataGridView dgv, DataGridViewCellPaintingEventArgs cellArgs, int minColIndex, int maxColIndex)
            {

int width = 0;//合并后单元格总宽度
                int height = cellArgs.CellBounds.Height;//合并后单元格总高度
               
                for (int i = minColIndex; i <= maxColIndex;i++ )
                {
                    width += ((Rectangle)rowSpan[i]).Width;
                }

Rectangle rectBegin = (Rectangle)rowSpan[minColIndex];//合并第一个单元格的位置信息
                Rectangle rectEnd = (Rectangle)rowSpan[maxColIndex];//合并最后一个单元格的位置信息
               
                //合并单元格的位置信息
                Rectangle reBounds = new Rectangle();
                reBounds.X = rectBegin.X;
                reBounds.Y = rectBegin.Y;
                reBounds.Width = width - 1;
                reBounds.Height = height - 1;

using (Brush gridBrush = new SolidBrush(dgv.GridColor),
                             backColorBrush = new SolidBrush(cellArgs.CellStyle.BackColor))
                {
                    using (Pen gridLinePen = new Pen(gridBrush))
                    {
                        // 画出上下两条边线，左右边线无
                        Point blPoint = new Point(rectBegin.Left, rectBegin.Bottom - 1);//底线左边位置
                        Point brPoint = new Point(rectEnd.Right - 1, rectEnd.Bottom - 1);//底线右边位置
                        cellArgs.Graphics.DrawLine(gridLinePen, blPoint, brPoint);//下边线

Point tlPoint = new Point(rectBegin.Left, rectBegin.Top);//上边线左边位置
                        Point trPoint = new Point(rectEnd.Right - 1, rectEnd.Top);//上边线右边位置
                        cellArgs.Graphics.DrawLine(gridLinePen, tlPoint, trPoint); //上边线

Point ltPoint = new Point(rectBegin.Left, rectBegin.Top);//左边线顶部位置
                        Point lbPoint = new Point(rectBegin.Left, rectBegin.Bottom - 1);//左边线底部位置
                        cellArgs.Graphics.DrawLine(gridLinePen, ltPoint, lbPoint); //左边线

Point rtPoint = new Point(rectEnd.Right - 1, rectEnd.Top);//右边线顶部位置
                        Point rbPoint = new Point(rectEnd.Right - 1, rectEnd.Bottom - 1);//右边线底部位置
                        cellArgs.Graphics.DrawLine(gridLinePen, rtPoint, rbPoint); //右边线

//计算绘制字符串的位置
                        SizeF sf = cellArgs.Graphics.MeasureString(rowValue, cellArgs.CellStyle.Font);
                        float lstr = (width - sf.Width) / 2;
                        float rstr = (height - sf.Height) / 2;

//画出文本框
                        if (rowValue != "")
                        {
                            cellArgs.Graphics.DrawString(rowValue, cellArgs.CellStyle.Font,
                                                       new SolidBrush(cellArgs.CellStyle.ForeColor),
                                                         rectBegin.Left + lstr,
                                                         rectBegin.Top + rstr,
                                                         StringFormat.GenericDefault);
                        }
                    }
                    cellArgs.Handled = true;
                }
                   
            }
        #endregion
    
    }
}

=======================================================
在DataGridView页面的DataGridView的CellPainting事件中写下下面代码就OK了

#region 统计行单元格绘制
        private void dgConfirm_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)
        {
            if (e.RowIndex!=-1  && dgConfirm.Rows[e.RowIndex].Cells[1].Value.ToString()==" "  )
            {
                e.CellStyle.Font = new Font(dgConfirm.DefaultCellStyle.Font, FontStyle.Bold);
                e.CellStyle.WrapMode = DataGridViewTriState.True;
                DGVOper.MerageRowSpan(dgConfirm, e, 1, 2);
            }
           
            //重绘统计行的选择框背景
            if ((e.RowIndex == dgConfirm.Rows.Count - 1) && (e.ColumnIndex==0))
            {
                Rectangle rect = new Rectangle();
                rect.X = e.CellBounds.X;
                rect.Y = e.CellBounds.Y;
                rect.Width = e.CellBounds.Width;
                rect.Height = e.CellBounds.Height;
                e.Paint(rect,DataGridViewPaintParts.ContentBackground);
                e.PaintBackground(rect,false);
                e.Handled = true;
          }
        }
        #endregion

怎么样效果行吗?但是沒有時間垂直合并的