生成Excel直接以流或字节形式发给客户端，无需在服务生成一个实体文件。

    public ActionResult ExportAgentBooking(string Company_Id, string Company_Name)//Altman.Web.BCDAdmin.Models.CompanyInfo argCompanyInfo)
        {
            if (string.IsNullOrWhiteSpace(Company_Id) || string.IsNullOrWhiteSpace(Company_Name))
            {
                return View();
            }

            Dictionary<string, object> vDic = new Dictionary<string, object>();
            vDic.Add("argCompanyId", Company_Id);//argCompanyInfo.Company_Id);
            vDic.Add("argStatus", (int)Altman.Web.Common.Utility.State.Active);
            vDic.Add("argGroupType", (int)Altman.Web.Common.Utility.GroupType.AgentBookingGroup);

            ClientResponse vUserInGroup = ExcuteService("Altman.Services.BCDAdmin.Group", "GetAgentBookingUser", vDic);
            DataTable vDT = vUserInGroup["DtUsers"] as DataTable;

            Common.ExcelHelper vExcelHelper = new ExcelHelper();
            MemoryStream vStream = vExcelHelper.ExeportAgentBookingData(vDT);
            if (vStream == null)
            {
                return View();  
            }
            string vFileName = string.Concat(Company_Name, ".xls");
            return File(vStream.ToArray(), CONTENTTYPE, vFileName);
        }

EXCEL处理类：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

using System.IO;
using NPOI.HSSF.UserModel;
using NPOI.SS.UserModel;
using System.Data;
namespace Altman.Web.BCDAdmin.Common
{

    public class ExcelHelper
    {
        public MemoryStream ExeportAgentBookingData(DataTable vDt)
        {
            vDt.DefaultView.Sort = "Group_Name desc,Agent_User_Id desc";
            vDt = vDt.DefaultView.ToTable();
            MemoryStream file = new MemoryStream();
            if (vDt == null || vDt.Rows.Count == 0)
            {
                return null; 
            }

            int vRowIndex = 0;
            HSSFWorkbook vHssfworkbook = new HSSFWorkbook();
            ISheet vSheet1 = vHssfworkbook.CreateSheet();//.GetSheetAt(0);
            IRow rowFirst = vSheet1.CreateRow(vRowIndex);
            rowFirst.CreateCell(0).SetCellValue("组名");
            rowFirst.CreateCell(1).SetCellValue("代订人 ");
            rowFirst.CreateCell(2).SetCellValue("被代订人 ");
            rowFirst.CreateCell(3).SetCellValue("Email");
            
            //设置sheet的属性
            for (int colCount = 0; colCount < 4; colCount++)
            {
                vSheet1.SetColumnWidth(colCount, 30* 256);
            }

                vRowIndex++;
            foreach(DataRow vRow in vDt.Rows)
            {
                IRow row = vSheet1.CreateRow(vRowIndex);
                string vUser_ID = vRow["User_ID"].AsString();
                string vAgent_User_Id = vRow["Agent_User_Id"].AsString();
                if (string.IsNullOrWhiteSpace(vUser_ID) && string.IsNullOrWhiteSpace(vAgent_User_Id))
                {
                    continue;
                }
                row.CreateCell(0).SetCellValue(vRow["Group_Name"].AsString());
                if(!string.IsNullOrWhiteSpace(vUser_ID))//被代订人 
                {
                    row.CreateCell(2).SetCellValue(vRow["User_Name"].AsString());
                }
                if(!string.IsNullOrWhiteSpace(vAgent_User_Id))//代订人 
                {
                    row.CreateCell(1).SetCellValue(vRow["User_Name"].AsString());
                }
                row.CreateCell(3).SetCellValue(vRow["User_Email"].AsString());
                vRowIndex++;
            }
            if (vRowIndex == 1)
            {
                return null;
            }
            vHssfworkbook.Write(file);
            return file;
        }
    }
}