gridview 固定多行表头如何固定 ，表头的融合是在.cs中写的

在.cs中的代码  protected void GridView1_RowCreated(object sender, GridViewRowEventArgs e)
    {
        switch (e.Row.RowType)
        {
            case DataControlRowType.Header:                TableCellCollection tcHeader = e.Row.Cells;
                tcHeader.Clear();                tcHeader.Add(new TableHeaderCell());
                tcHeader[0].Attributes.Add("bgcolor", "LightSteelBlue");
                tcHeader[0].Style.Add("BACKGROUND-COLOR", "#0099cc");
                tcHeader[0].Attributes.Add("rowspan", "2");
                tcHeader[0].Text = "序号";
                tcHeader.Add(new TableHeaderCell());
                tcHeader[1].Attributes.Add("bgcolor", "LightSteelBlue");
                tcHeader[1].Style.Add("BACKGROUND-COLOR", "#0099cc");
                tcHeader[1].Attributes.Add("rowspan", "2");
                tcHeader[1].Text = "选择";                tcHeader.Add(new TableHeaderCell());
                tcHeader[2].Attributes.Add("bgcolor", "LightSteelBlue");
                tcHeader[2].Style.Add("BACKGROUND-COLOR", "#0099cc");
                tcHeader[2].Style.Add("width", "20%");
                tcHeader[2].Attributes.Add("rowspan", "2");
                tcHeader[2].Text = " 名称  ";                tcHeader.Add(new TableHeaderCell());
                tcHeader[3].Attributes.Add("bgcolor", "LightSteelBlue");
                tcHeader[3].Style.Add("BACKGROUND-COLOR", "#0099cc");
                tcHeader[3].RowSpan = 2;
                tcHeader[3].Text = "规格型号";
                tcHeader.Add(new TableHeaderCell());
                tcHeader[4].Attributes.Add("bgcolor", "LightSteelBlue");
                tcHeader[4].Style.Add("position", "relative");
                tcHeader[4].Style.Add("BACKGROUND-COLOR", "#0099cc");
                tcHeader[4].RowSpan = 2;
                tcHeader[4].Text = "批号";                tcHeader.Add(new TableHeaderCell());
                tcHeader[5].Attributes.Add("bgcolor", "LightSteelBlue");
                tcHeader[5].Style.Add("BACKGROUND-COLOR", "#0099cc");
                tcHeader[5].RowSpan = 2;
                tcHeader[5].Text = "资金编号";
                tcHeader.Add(new TableHeaderCell());
                tcHeader[6].Attributes.Add("bgcolor", "LightSteelBlue");
                tcHeader[6].Style.Add("BACKGROUND-COLOR", "#0099cc");
                tcHeader[6].RowSpan = 2;
                tcHeader[6].Text = "状态";
                tcHeader.Add(new TableHeaderCell());
                tcHeader[7].ColumnSpan = 3;
                tcHeader[7].Text = "计划下达";
                tcHeader.Add(new TableHeaderCell());
                tcHeader[8].ColumnSpan = 3;
                tcHeader[8].Text = "预计完成情况";                tcHeader.Add(new TableHeaderCell());
                tcHeader[9].ColumnSpan = 3;
                tcHeader[9].Text = "合同情况";                tcHeader.Add(new TableHeaderCell());
                tcHeader[10].ColumnSpan = 3;
                tcHeader[10].Text = "结算情况";                tcHeader.Add(new TableHeaderCell());
                tcHeader[11].Attributes.Add("bgcolor", "LightSteelBlue");
                tcHeader[11].Style.Add("BACKGROUND-COLOR", "#0099cc");
                tcHeader[11].RowSpan = 2;
                tcHeader[11].Text = "是否含税";
                tcHeader.Add(new TableHeaderCell());
                tcHeader[12].Attributes.Add("bgcolor", "LightSteelBlue");
                tcHeader[12].Style.Add("BACKGROUND-COLOR", "#0099cc");
                tcHeader[12].RowSpan = 2;
                tcHeader[12].Text = "税率(%)";                tcHeader.Add(new TableHeaderCell());
                tcHeader[13].Attributes.Add("bgcolor", "LightSteelBlue");
                tcHeader[13].Style.Add("BACKGROUND-COLOR", "#0099cc");
                tcHeader[13].RowSpan = 2;
                tcHeader[13].Text = "税额";
                tcHeader.Add(new TableHeaderCell());
                tcHeader[14].Attributes.Add("bgcolor", "LightSteelBlue");
                tcHeader[14].Style.Add("BACKGROUND-COLOR", "#0099cc");
                tcHeader[14].RowSpan = 2;
                tcHeader[14].Text = "税后金额";                tcHeader.Add(new TableHeaderCell());
                tcHeader[15].Attributes.Add("bgcolor", "LightSteelBlue");
                tcHeader[15].Style.Add("position", "relative");
                tcHeader[15].Style.Add("TOP", "expression(this.offsetParent.scrollTop-2)");
                tcHeader[15].Style.Add("BACKGROUND-COLOR", "#0099cc");
                tcHeader[15].Style.Add("z-index", "1");
                tcHeader[15].RowSpan = 2;
                tcHeader[15].Text = "使用单位<br/>或储备单位";
                tcHeader.Add(new TableHeaderCell());
                tcHeader[16].Attributes.Add("bgcolor", "LightSteelBlue");
                tcHeader[16].Style.Add("BACKGROUND-COLOR", "#0099cc");
                tcHeader[16].RowSpan = 2;
                tcHeader[16].Text = "购置理由";
                tcHeader.Add(new TableHeaderCell());
                tcHeader[17].Attributes.Add("bgcolor", "LightSteelBlue");
                tcHeader[17].Style.Add("BACKGROUND-COLOR", "#0099cc");
                tcHeader[17].RowSpan = 2;
                tcHeader[17].Text = "购置详细理由";                tcHeader.Add(new TableHeaderCell());
                tcHeader[18].Attributes.Add("bgcolor", "LightSteelBlue");
                tcHeader[18].Style.Add("BACKGROUND-COLOR", "#0099cc");
                tcHeader[18].RowSpan = 2;
                tcHeader[18].Text = "生产厂家<br/>或施工单位";                tcHeader.Add(new TableHeaderCell());
                tcHeader[19].Attributes.Add("bgcolor", "LightSteelBlue");
                tcHeader[19].Style.Add("position", "relative");
                tcHeader[19].Style.Add("BACKGROUND-COLOR", "#0099cc");
                tcHeader[19].RowSpan = 2;
                tcHeader[19].Text = "市场准入证号<br/>或油田单位</th></tr><tr>";
                //计划下达
                tcHeader.Add(new TableHeaderCell());
                tcHeader[20].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[20].Text = "单价<br/>（元）";                tcHeader.Add(new TableHeaderCell());
                tcHeader[21].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[21].Text = "数量";                tcHeader.Add(new TableHeaderCell());
                tcHeader[22].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[22].Text = "金额<br/>（元）";
                //完成情况
                tcHeader.Add(new TableHeaderCell());
                tcHeader[23].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[23].Text = "单价<br/>（元）";                tcHeader.Add(new TableHeaderCell());
                tcHeader[24].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[24].Text = "数量";                tcHeader.Add(new TableHeaderCell());
                tcHeader[25].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[25].Text = "金额<br/>（元）";
                //合同情况
                tcHeader.Add(new TableHeaderCell());
                tcHeader[26].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[26].Text = "单价<br/>（元）";                tcHeader.Add(new TableHeaderCell());
                tcHeader[27].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[27].Text = "数量";                tcHeader.Add(new TableHeaderCell());
                tcHeader[28].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[28].Text = "金额<br/>（元）";                //结算情况
                tcHeader.Add(new TableHeaderCell());
                tcHeader[29].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[29].Text = "单价<br/>（元）";                tcHeader.Add(new TableHeaderCell());
                tcHeader[30].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[30].Text = "数量";                tcHeader.Add(new TableHeaderCell());
                tcHeader[31].Attributes.Add("bgcolor", "DarkSeaGreen");
                tcHeader[31].Text = "金额<br/>（元）";
                break;
        }
    }