.Net core NPOI导入导出Excel

using NPOI.HSSF.UserModel;
using NPOI.SS.UserModel;
using NPOI.XSSF.UserModel;

  /// <summary>
        /// 导出列表
        /// </summary>
        /// <returns></returns>
        public void GetExportList()
        {
            //取出数据源
            var exportList = db.Reg_Message
                .Select(u => new
                {
                    u.UserName,
                    u.Mobile,
                    u.Content,
                    u.CreateDate
                }).ToList();

            HSSFWorkbook book = new HSSFWorkbook();
            ISheet s1 = book.CreateSheet("留言列表");
            IRow r1 = s1.CreateRow(0);
            r1.CreateCell(0).SetCellValue("用户");
            r1.CreateCell(1).SetCellValue("手机号");
            r1.CreateCell(2).SetCellValue("留言内容");
            r1.CreateCell(3).SetCellValue("留言日期");
            for (int i = 0; i < exportList.Count; i++)
            {
                NPOI.SS.UserModel.IRow rt = s1.CreateRow(i + 1);
                rt.CreateCell(0).SetCellValue(exportList[i].UserName);
                rt.CreateCell(1).SetCellValue(exportList[i].Mobile);
                rt.CreateCell(2).SetCellValue(exportList[i].Content);
                rt.CreateCell(3).SetCellValue(exportList[i].CreateDate);
            }

            var path = ConfigHelper.GetValue("ExportPath");
            if (!Directory.Exists(path))
            {
                Directory.CreateDirectory(path);
            }
            FileStream stream = new FileStream(path + DateTime.Now.ToString("yyyyMMddhhmmssffff") + ".xls", FileMode.CreateNew);
            book.Write(stream);
            stream.Seek(0, SeekOrigin.Begin);
            book.Close();
            stream.Close();
        }

    //导出
    function btn_export() {
        //location.href = "../../RegManage/Message/ExportList";
        $.ConfirmAjax({
                msg: "注：您确定要导出吗？",
                url: "/RegManage/Message/ExportList",
                success: function (data) {
                    $("#gridTable").trigger("reloadGrid");
                }
        })
    }