GridView合并表头多重表头

最近在工作中遇到一个要合并表头的统计报表：下面是实现代码，刚开始我以为同合并Table一样，没想到GridView是按每行顺序来的，只在每行要进合并的地方做改变。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
using System.Text;
using System.IO;

public partial class web_hr_kaoqin_report_ChuChaiStatistic : System.Web.UI.Page
{
    private string selectstr = null;
    private string searchName = "select [姓名],[员工编码],[部门],[开始日期],[终止日期] from [WEC].[KaoQin].[请假表] where [姓名] like '%'+@wherestr+'%'";
    // private string searchTimeStartEnd = "select top 10 [姓名],[员工编码],[部门] from [请假表] where [开始日期]>=@startdate and [终止日期]<=@enddate";
    private string searchBmName = "select [姓名],[员工编码],[部门] from [WEC].[KaoQin].[请假表] where [部门]=@wherestr";
    // private string searchXmName = "select select top 10 [姓名],[员工编码],[部门] from [请假表]";
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            BmName();        
            Bind();
        }
    }
    private void BmName()
    {
        string sqlbm = "select [部门名称] from [WEC].[HR].[部门]";
        DataTable dt = DBHelper.GetDataSet(sqlbm);
        for (int i = 0; i < dt.Rows.Count; i++)
        {
            DropDownList1.Items.Add(dt.Rows[i][0].ToString());
        }        
    }
    private void XmName() 
    {
    
    }
    private void Bind()
    {
        string sqlstr = "select top 10 [姓名],[员工编码],[部门] from WEC.KaoQin.请假表";
        DataTable dt = DBHelper.GetDataSet(sqlstr);
        GridView1.DataSource = dt;
        GridView1.DataBind();
    }
  
//下面的事件就是GridView合并表头的解决方案哦！

/// <summary>
    ///GridView合并表头
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    protected void GridView1_RowCreated(object sender, GridViewRowEventArgs e)
    {
        switch (e.Row.RowType)
        {
            case DataControlRowType.Header:

                TableCellCollection tcHeader = e.Row.Cells;
                tcHeader.Clear();

                //第一行表头
                tcHeader.Add(new TableHeaderCell());
                //tcHeader[0].Attributes.Add("bgcolor", "blue");
                tcHeader[0].Attributes.Add("colspan", "18"); //跨Column
                tcHeader[0].Text = "出差统计报表</th></tr><tr>";

                //第二行表头
                tcHeader.Add(new TableHeaderCell());
                //tcHeader[1].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[1].Attributes.Add("rowspan", "3"); //跨Row
                tcHeader[1].Text = "序号";
                tcHeader.Add(new TableHeaderCell());
               // tcHeader[2].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[2].Attributes.Add("rowspan", "3");
                tcHeader[2].Text = "姓&nbsp;&nbsp;&nbsp;&nbsp;名";
                tcHeader.Add(new TableHeaderCell());
                //tcHeader[3].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[3].Attributes.Add("rowspan", "3");
                tcHeader[3].Text = "员工编码";
                tcHeader.Add(new TableHeaderCell());
               // tcHeader[4].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[4].Attributes.Add("rowspan", "3");
                tcHeader[4].Text = "部门";
                tcHeader.Add(new TableHeaderCell());
               // tcHeader[5].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[5].Attributes.Add("rowspan", "3");
                tcHeader[5].Text = "专业";
                tcHeader.Add(new TableHeaderCell());
               // tcHeader[6].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[6].Attributes.Add("colspan", "6");
                tcHeader[6].Text = "出差类型";
                tcHeader.Add(new TableHeaderCell());
               // tcHeader[7].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[7].Attributes.Add("rowspan", "3");
                tcHeader[7].Text = "项目简称";
                tcHeader.Add(new TableHeaderCell());
               // tcHeader[8].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[8].Attributes.Add("rowspan", "3");
                tcHeader[8].Text = "出差事由";
                tcHeader.Add(new TableHeaderCell());
               // tcHeader[9].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[9].Attributes.Add("rowspan", "3");
                tcHeader[9].Text = "出差地点";
                tcHeader.Add(new TableHeaderCell());
               // tcHeader[10].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[10].Attributes.Add("rowspan", "3");
                tcHeader[10].Text = "计划出差起止时间";
                tcHeader.Add(new TableHeaderCell());
               // tcHeader[11].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[11].Attributes.Add("rowspan", "3");
                tcHeader[11].Text = "计划出差天数";
                tcHeader.Add(new TableHeaderCell());
               // tcHeader[12].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[12].Attributes.Add("rowspan", "3");
                tcHeader[12].Text = "实际出差起止时间";
                tcHeader.Add(new TableHeaderCell());
               // tcHeader[13].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[13].Attributes.Add("rowspan", "3");
                tcHeader[13].Text = "实际出差天数</th></tr><tr>";


                //第三行表头
                tcHeader.Add(new TableHeaderCell());
               // tcHeader[14].Attributes.Add("bgcolor", "Aqua");
                tcHeader[14].Attributes.Add("rowspan", "2");
                tcHeader[14].Text = "项目出差";
                tcHeader.Add(new TableHeaderCell());
               // tcHeader[15].Attributes.Add("bgcolor", "Aqua");
                tcHeader[15].Attributes.Add("rowspan", "2");
                tcHeader[15].Text = "经营出差";
                tcHeader.Add(new TableHeaderCell());
               // tcHeader[16].Attributes.Add("bgcolor", "Aqua");
                tcHeader[16].Attributes.Add("colspan", "4");
                tcHeader[16].Text = "非项目出差</th></tr><tr>";

                //第四行
                tcHeader.Add(new TableHeaderCell());
               // tcHeader[17].Attributes.Add("bgcolor", "Gray");
                tcHeader[17].Text = "一般性出差";
                tcHeader.Add(new TableHeaderCell());
               // tcHeader[18].Attributes.Add("bgcolor", "Gray");
                tcHeader[18].Text = "各类会议";
                tcHeader.Add(new TableHeaderCell());
               // tcHeader[19].Attributes.Add("bgcolor", "Gray");
                tcHeader[19].Text = "培训";
                tcHeader.Add(new TableHeaderCell());
               // tcHeader[20].Attributes.Add("bgcolor", "Gray");
                tcHeader[20].Text = "其它";
                break;
        }
    } 

    protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
    {        
        //如果是绑定数据行
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            //鼠标经过时，行背景色变 
            e.Row.Attributes.Add("onmouseover", "this.style.backgroundColor='#E6F5FA'");
            //鼠标移出时，行背景色变 
            e.Row.Attributes.Add("onmouseout", "this.style.backgroundColor='#FFFFFF'");
        }
        if (e.Row.RowIndex != -1)
        {
            int id = e.Row.RowIndex + 1;
            e.Row.Cells[0].Text = id.ToString();//Gridview自动生成序号
           // e.Row.Cells[15].Text=dt2.Rows[id][3].ToString()+"--"+dt2.Rows[id][4].ToString();
        }
    }
    protected void lnkBtnCreateExcel_Click(object sender, EventArgs e)
    {
        Export("application/ms-excel", "出差统计报表.xls");
    }

    /// <summary>
    /// GridView导出为excel
    /// </summary>
    /// <param name="FileType">导出的文件类型</param>
    /// <param name="FileName">导出文件名称</param>
    private void Export(string FileType, string FileName)
    {
        Response.Charset = "GB2312";
        Response.ContentEncoding = Encoding.UTF7;
        Response.AppendHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(FileName, Encoding.UTF8).ToString());
        Response.ContentType = FileType;
        this.EnableViewState = false;
        StringWriter tw = new StringWriter();
        HtmlTextWriter hw = new HtmlTextWriter(tw);
        GridView1.RenderControl(hw);
        Response.Write(tw.ToString());
        Response.End();
    }
    public override void VerifyRenderingInServerForm(Control control)
    {
    }
    
    protected void btnSearch_Click(object sender, EventArgs e)
    {
        string fsstrv = Request.Form["sele"].ToString();
        //Response.Write("<script>alert('" + fsstrv + "');</script>");
        
        SqlParameter[] param = new SqlParameter[1];
        param[0] = new SqlParameter("@wherestr", SqlDbType.VarChar);
        param[0].Value = null;
        switch (fsstrv)
        {
            case "0":
                Bind();
                break;
            case "1":
                selectstr = searchName;
                param[0].Value = TxtName.Text.Trim();
                break;
            case "2":
                //selectstr = searchTimeStartEnd;
                Bind();
                break;
            case "3":
                selectstr = searchBmName;
                param[0].Value = DropDownList1.SelectedValue;
                break;
            case "4":
                //selectstr = searchXmName;
                Bind();
                break;
        }
        DataTable dt = DBHelper.GetDataSet(selectstr, param);
        GridView1.DataSource = dt;
        GridView1.DataBind();
    }
}

 下面是效果图：