DataTable数据导出到Excel，并发送到客户端进行下载

本代码实现思路是：页面显示和导出分开，导出的数据和用于页面显示的是同一查询数据方式，所以也是同样的数据，只是在导出数据时从数据库重新捞了一次数据。
此导出数据方式会先将数据保存到Excel中，然后将创建的Excel文件保存到服务器指定位置，然后下载到客户端，下载完后立即删除掉刚在服务器上创建的Excel文件。

// 导出按钮事件

protected void btOutputData_Click(object sender, EventArgs e)
    {
        ExportExcel(GetPrintingData(ViewState["ssearchCondition"].ToString()), Convert.ToInt32(ConfigurationManager.AppSettings["OutputData        PageSize"].ToString()));
    }

#region   导出数据
    /// <summary>
    /// 获取需要导出的数据
    /// </summary>
    /// <param name="strWhere">筛选数据的条件</param>
    /// <returns></returns>
    public System.Data.DataTable GetPrintingData(string strWhere)
    {
        System.Data.DataTable dt = GetListByPage(strWhere, , GetRecordCount(ViewState["ssearchCondition"].ToString()));
        System.Data.DataTable newTable = new System.Data.DataTable();
        newTable.Columns.AddRange(new DataColumn[]{
                    new DataColumn("rowN"),
                    new DataColumn("Description"),
                    new DataColumn("area"),
                    new DataColumn("projectName"),
                    new DataColumn("stake"),

                    new DataColumn("itemProjectName"),
                    new DataColumn("newCol2"),
                    new DataColumn("newCol3"),
                    new DataColumn("newCol4"),
                    new DataColumn("newCol5"),

                    new DataColumn("newCol6"),
                    new DataColumn("newCol7"),
                    new DataColumn("acceptConclution_zdb"),
                    new DataColumn("newCol8"),
                    new DataColumn("acceptConclution_zjb"),

                    new DataColumn("joinAccept_yz"),
                    new DataColumn("joinAccept_zjb"),
                    new DataColumn("joinAccept_zdb"),
                    new DataColumn("joinAccept_xmb")});
        int num = ;
        for (int i = ; i < dt.Rows.Count; i++)
        {
            DataRow newRow = newTable.NewRow();
            newRow["rowN"] = num++;// dt.Rows[i]["rowN"];
            newRow["Description"] = dt.Rows[i]["Description"];
            newRow["area"] = dt.Rows[i]["area"];
            newRow["projectName"] = dt.Rows[i]["projectName"];
            newRow["stake"] = dt.Rows[i]["stake"];

            newRow["itemProjectName"] = dt.Rows[i]["itemProjectName"];
            newRow["newCol2"] = dt.Rows[i]["newCol2"];
            newRow["newCol3"] = dt.Rows[i]["newCol3"];
            newRow["newCol4"] = dt.Rows[i]["newCol4"];
            newRow["newCol5"] = dt.Rows[i]["newCol5"];

            newRow["newCol6"] = dt.Rows[i]["newCol6"];
            newRow["newCol7"] = dt.Rows[i]["newCol7"];
            newRow["acceptConclution_zdb"] = dt.Rows[i]["acceptConclution_zdb"];
            newRow["newCol8"] = dt.Rows[i]["newCol8"];
            newRow["acceptConclution_zjb"] = dt.Rows[i]["acceptConclution_zjb"];

            newRow["joinAccept_yz"] = dt.Rows[i]["joinAccept_yz"];
            newRow["joinAccept_zjb"] = dt.Rows[i]["joinAccept_zjb"];
            newRow["joinAccept_zdb"] = dt.Rows[i]["joinAccept_zdb"];
            newRow["joinAccept_xmb"] = dt.Rows[i]["joinAccept_xmb"];
            newTable.Rows.Add(newRow);
        }
        return newTable;
    }
    /// <summary>
    /// 把table中的数据导出到excel中去
    /// </summary>
    /// <param name="dt">要导入的table</param>
    /// <param name="maxcount">模板excel中，一个sheet要显示的行数,如果数据多一个sheet中的最大值，会自动生成新的sheet</param>
    private void ExportExcel(System.Data.DataTable dt, int maxcount)
    {
        Random ran = new Random();
        string fileautoname = Server.MapPath("~/") + DateTime.Now.ToString("yyyyMMddhhmmss") + ran.Next(, ) + ".xls";//给新文件命名
        string filepath = Server.MapPath("/") + "UpLoadFile\\Template\\OutputDataBlock.xls"; //模板文件路径
        object missing = Type.Missing;
        Microsoft.Office.Interop.Excel.Application application = new Application();
        Workbook workbook = application.Workbooks.Open(filepath, missing, missing, missing, missing, missing, missing, missing, missing, missing, missing, missing, missing, missing, missing);
        Worksheet worksheet;
        worksheet = (Worksheet)workbook.Sheets.get_Item();
        //DataView dv = dt.DefaultView;
        //dv.Sort = "id asc"; //table 中的数据按id升序排列
        //System.Data.DataTable table = dv.ToTable();
        System.Data.DataTable table = dt;
        int sheetcount = GetSheetCount(table.Rows.Count, maxcount);
        for (int count = ; count < sheetcount; count++)
        {
            ((Microsoft.Office.Interop.Excel.Worksheet)workbook.Worksheets.get_Item(count)).Copy(missing, workbook.Worksheets[count]);
        }
        List<object[,]> list = new List<object[,]>();
        object[,] ret;
        for (int count = ; count < sheetcount; count++)
        {
            if (count == sheetcount - )
            {
                ret = new object[table.Rows.Count - count * maxcount, table.Columns.Count - ];
                for (int i = ; i < table.Rows.Count - count * maxcount; i++)
                {
                    for (int j = ; j < table.Columns.Count - ; j++)
                    {
                        ret[i, j] = table.Rows[count * maxcount + i][j];
                    }
                }
                list.Add(ret);
            }
            else
            {
                ret = new object[maxcount, table.Columns.Count - ];
                for (int i = ; i < maxcount; i++)
                {
                    for (int j = ; j < table.Columns.Count - ; j++)
                    {
                        ret[i, j] = table.Rows[i + count * maxcount][j];
                    }
                }
                list.Add(ret);
            }
        }

        object[,] obj;
        for (int p = ; p < list.Count; p++)
        {
            worksheet = (Worksheet)workbook.Sheets.get_Item(p + );
            obj = list[p];
            string cn = "L" + (obj.GetLength() + ).ToString(); //设置填充区域
            worksheet.get_Range("A3", cn).FormulaR1C1 = obj;
        }
        workbook.SaveAs(fileautoname, missing, missing, missing, missing, missing, Microsoft.Office.Interop.Excel.XlSaveAsAccessMode.xlNoChange, missing, missing, missing, missing, missing);
        workbook.Close(missing, missing, missing);
        application.Quit();
        workbook = null;

        #region
        System.IO.FileInfo file = new System.IO.FileInfo(fileautoname);
        Response.Clear();
        Response.Charset = "GB2312";
        Response.ContentEncoding = System.Text.Encoding.UTF8;
        // 添加头信息，为"文件下载/另存为"对话框指定默认文件名
        Response.AddHeader("Content-Disposition", "attachment; filename=" + Server.UrlEncode(file.Name));
        // 添加头信息，指定文件大小，让浏览器能够显示下载进度
        Response.AddHeader("Content-Length", file.Length.ToString());

        // 指定返回的是一个不能被客户端读取的流，必须被下载
        Response.ContentType = "application/ms-excel";

        // 把文件流发送到客户端
        Response.WriteFile(file.FullName);
        Response.Flush();//这个语句必须有，否则就不回弹出保存的对话框，搞了N久 

        //删除长生的临时Excel文件
        string filePath = fileautoname;//获取文件路径
        if (filePath != null && System.IO.File.Exists(filepath))
        {
            //判断文件是否存在，如果存在，就删除之
            System.IO.File.Delete(filePath);
        }

        // 停止页面的执行
        Response.End();
        #endregion
    }
    /// <summary>
    ///  获取WorkSheet数量
    /// </summary>
    /// <param name="rowCount">记录总行数</param>
    /// <param name="rows">每WorkSheet行数</param>
    /// <returns></returns>
    private int GetSheetCount(int rowCount, int rows)
    {
        int n = rowCount % rows;        //余数

        if (n == )
            return rowCount / rows;
        else
            return Convert.ToInt32(rowCount / rows) + ;
    }

    #endregion