asp.net 输出(导出) excel 文件（实用）

        /// <summary>
        /// 商品导出Excel
        /// </summary>
        /// <returns></returns>
       public ActionResult ProjectToExcel()
        {
            string subjectNo = Request.Params["SNo"] ?? "";
            if (!string.IsNullOrEmpty(subjectNo))
            {
                SWfsSubjectService service = new SWfsSubjectService();
                IList<ProductInfo> productList = service.GetProductList(subjectNo.Trim());
                List<ProductInfo> list = new List<ProductInfo>();
                if (productList != null)
                    list = productList.ToList();

                //获取当前活动下的所有分组
                IList<SWfsSubjectCategory> categoryList = service.GetSWfsSubjectProductList(subjectNo.Trim());
                string tempCategoryNo = string.Empty;
                if (categoryList != null)
                {
                    //判断分组情况，单组情况按以前排序
                    if (categoryList.Count == 1)
                    {
                        #region 无分组排序
                        tempCategoryNo = categoryList[0].CategoryNo;
                        IList<SWfsSubjectProductSort> sortList = service.GetProductSortList(tempCategoryNo);

                        List<ProductInfo> tmplList = list;
                        if (sortList.Count > 0)
                        {
                            list = (from l in productList
                                    join s in sortList on l.ProductNo equals s.ProductNo
                                    orderby s.Sort ascending
                                    select l).ToList();
                        }
                        if (list.Count < tmplList.Count)
                        {
                            tmplList = (from t in tmplList
                                        where !(from b in list select b.ProductNo).Contains(t.ProductNo)
                                        select t).ToList();
                            list.AddRange(tmplList);
                        } 
                        #endregion
                    }
                    else   // 分组情况，拆分成单组情况排序，分组顺序依照显示遍历
                    {
                        #region 分组排序
                        //单分组
                        List<ProductInfo> singleList = new List<ProductInfo>();
                        //聚合全部数据
                        List<ProductInfo> ListSum = new List<ProductInfo>();

                        //为防止多次访问数据库，直接查出所有分组数据
                        IList<SWfsSubjectProductSort> sortList = new List<SWfsSubjectProductSort>();
                        foreach (var model in categoryList)
                        {
                            tempCategoryNo += model.CategoryNo + ",";
                            sortList = service.GetProductSortList(tempCategoryNo);
                        }

                        //循环各组，拆分
                        foreach (var model in categoryList)
                        {
                            IList<SWfsSubjectProductSort> TempSortList = sortList.Where(c => c.SubjectNo == model.CategoryNo).ToList();

                            if (TempSortList != null && TempSortList.Count > 0)
                            {
                                //查出当前分组里面的所有商品
                                List<ProductInfo> singleALLList = productList.Where(c => c.CategoryNo == model.CategoryNo).ToList();

                                //排序的插入
                                singleList = (from l in singleALLList
                                              join s in TempSortList on l.ProductNo equals s.ProductNo
                                              orderby s.Sort ascending
                                              select l).ToList();
                                ListSum.AddRange(singleList);

                                //判断是否有无排序的，如果有，提取插入
                                if (singleList.Count < singleALLList.Count)
                                {
                                    singleList = (from t in singleALLList
                                                  where !(from b in singleList select b.ProductNo).Contains(t.ProductNo)
                                                  select t).ToList();
                                    ListSum.AddRange(singleList);
                                }

                            }
                            else
                            {
                                //无分排序直接插入
                                ListSum.AddRange(productList.Where(c => c.CategoryNo == model.CategoryNo).ToList());
                            }
                        }
                        list = ListSum; 
                        #endregion
                    }
                }
                //判断当前商品数据，如果有数据那么可以导出，如果无数据，判断返回
                if (list.Count > 0)
                {
                    byte[] fileContents = Encoding.UTF8.GetBytes(ExcelMsg(subjectNo, list));
                    var fileStream = new MemoryStream(fileContents);
                    string excelname = "活动：" + subjectNo + "日期：" + DateTime.Now + ".xls";
                    return File(fileStream, "application/ms-excel", excelname);
                }
                else
                {
                    string TempAlert = string.Format("<script>alert(‘当前分组无商品数据！‘);history.back(-1);</script>");
                    return Content(TempAlert, "text/html");
                }
            }
            return View();
        }

        private string ExcelMsg(string subjectNo, IList<ProductInfo> productList)
        {
            #region 获取活动名称
            SWfsSubjectService service = new SWfsSubjectService();
            IList<SWfsSubject> subjectEntity = service.GetSWfsSubjectBySubjectNo(subjectNo);
            string sujectName = string.Empty;
            if (subjectEntity != null && subjectEntity.Count() > 0)
                sujectName = string.IsNullOrEmpty(subjectEntity[0].SubjectName) ? subjectEntity[0].SubjectEnName : subjectEntity[0].SubjectName;
            #endregion
            StringBuilder sb = new StringBuilder("<table width=\"100%\"><tr><td colspan=\"10\" rowspan=\"2\"><h2 width=\"100%\">活动名称：" + sujectName + "</h2></td></tr></table><h2>活动编号：" + subjectNo + "</h2><h2>活动商品</h2><table cellpadding=\"0\" cellspacing=\"0\" border=\"1\"  width=\"758px\" id=\"AccountListTable\" >");

            sb.AppendLine("<tr style=\"background-color:#FFFF00;\">");
            sb.AppendLine("<td><span>分组名称</span></td>");
            sb.AppendLine("<td><span>商品编号</span></td>");
            sb.AppendLine("<td><span>商品名</span></td>");
            sb.AppendLine("<td><span>品牌</span></td> ");
            sb.AppendLine("</tr>");
            foreach (ProductInfo psingle in productList)
            {
                #region 导出excel格式模板
                string brandName = string.IsNullOrEmpty(psingle.BrandEnName) == true ? psingle.BrandCnName : psingle.BrandEnName;
                sb.AppendLine("<tr align=\"left\">");
                sb.AppendLine(String.Format("<td>{0}</td>", psingle.CategoryName));
                sb.AppendLine(String.Format("<td style=\"mso-number-format:\\@;\">{0}</td>", psingle.ProductNo));
                sb.AppendLine(String.Format("<td>{0}</td>", psingle.ProductName));
                sb.AppendLine(String.Format("<td>{0}</td>", brandName));
                sb.AppendLine("</tr>");
                #endregion
            }

            sb.AppendLine("</table>");
            return sb.ToString();
        }