DataTable 更改在有数据列的类型方法+DataTable 导出excel功能

 /// <summary>
    /// 导出功能
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    protected void btn_export_Click(object sender, EventArgs e)
    {
        try
        {
            string strSql = CreateStrWhere();
            DataTable dst = ShDonBLL.GetListForEXport(strSql).Tables[0];
            if (dst.Rows.Count<=0)
            {
                Jscript.Alert(this, "查询数据为空，没有数据导出，请重新选择条件！");
                return;
            }
            DataTable ds = UpdateDataTable(dst);
            for (int i = 0; i < ds.Rows.Count; i++)
            {
                DataColumn dc = ds.Columns[1];//i就是第几列或者用列名也可以
                dc.DataType = typeof(String);
                string eid = ds.Rows[i]["装置名称"].ToString();
                string tyid = ds.Rows[i]["类别"].ToString();
                if (!string.IsNullOrEmpty(eid))
                {
                    ds.Rows[i]["装置名称"] = GetEqui(eid);
                }
                if (!string.IsNullOrEmpty(tyid))
                {
                    ds.Rows[i]["类别"] = GetZG(tyid);
                }
            }
            //DataTableExcel(ds,"测试0","");

        }
        catch (Exception ex)
        {

            throw ex;
        }
    }
    /// <summary>
    /// 修改数据表DataTable某一列的类型和记录值(正确步骤：1.克隆表结构，2.修改列类型，3.修改记录值，4.返回希望的结果)
    /// </summary>
    /// <param name="argDataTable">数据表DataTable</param>
    /// <returns>数据表DataTable</returns>  

    private DataTable UpdateDataTable(DataTable argDataTable)
    {
        DataTable dtResult = new DataTable();
        //克隆表结构
        dtResult = argDataTable.Clone();
        foreach (DataColumn col in dtResult.Columns)
        {
            if (col.ColumnName == "装置名称" || col.ColumnName == "类别")
            {
                //修改列类型
                col.DataType = typeof(String);
            }
        }
        foreach (DataRow row in argDataTable.Rows)
        {
            DataRow rowNew = dtResult.NewRow();
            rowNew["序号"] = row["序号"];
            rowNew["装置名称"] = row["装置名称"];
            rowNew["停工时间"] = row["停工时间"];
            rowNew["开工时间"] = row["开工时间"];
            rowNew["正常时间"] = row["正常时间"];
            rowNew["停工原因"] = row["停工原因"];
            rowNew["类别"] = row["类别"];
            rowNew["停工时间小时"] = row["停工时间小时"];
            rowNew["年度"] = row["年度"];
            dtResult.Rows.Add(rowNew);
        }
        return dtResult;
    }

    #region  DataTable导出到Excel
    /// <summary>
    /// DataTable导出到Excel
    /// </summary>
    /// <param name="pData">DataTable</param>
    /// <param name="pFileName">导出文件名</param>
    /// <param name="pHeader">导出标题以|分割</param>
    public static void DataTableExcel(System.Data.DataTable pData, string pFileName, string pHeader)
    {
        System.Web.UI.WebControls.DataGrid dgExport = null;
        // 当前对话 
        System.Web.HttpContext curContext = System.Web.HttpContext.Current;
        // IO用于导出并返回excel文件 
        System.IO.StringWriter strWriter = null;
        System.Web.UI.HtmlTextWriter htmlWriter = null;
        if (pData != null)
        {
            string UserAgent = curContext.Request.ServerVariables["http_user_agent"].ToLower();
            if (UserAgent.IndexOf("firefox") == -1)//火狐浏览器
                pFileName = HttpUtility.UrlEncode(pFileName, System.Text.Encoding.UTF8);
            curContext.Response.AddHeader("Content-Disposition", "attachment; filename=" + pFileName + ".xls");
            curContext.Response.ContentType = "application/vnd.ms-excel";
            strWriter = new System.IO.StringWriter();
            htmlWriter = new System.Web.UI.HtmlTextWriter(strWriter);
            // 为了解决dgData中可能进行了分页的情况，需要重新定义一个无分页的DataGrid 
            dgExport = new System.Web.UI.WebControls.DataGrid();
            dgExport.DataSource = pData.DefaultView;
            dgExport.AllowPaging = false;
            dgExport.ShowHeader = true;//显示标题
            dgExport.DataBind();
            string[] arrHeader = pHeader.Split('|');
            string strHeader = "<table border=\"1\" style=\"background-color:Gray;font-weight:bold;\"><tr>";
            foreach (string j in arrHeader)
            {
                strHeader += "<td>" + j.ToString() + "</td>";
            }
            strHeader += "</tr></table>";
            // 返回客户端 
            dgExport.RenderControl(htmlWriter);
            string strMeta = "<meta http-equiv=\"content-type\" content=\"application/ms-excel; charset=UTF-8\"/>";
            curContext.Response.Write(strMeta + strHeader + strWriter.ToString());
            curContext.Response.End();
        }
    }