C# LINQ 生成List<T>交叉表数据

        /// <summary>
        /// 费用一览表报表
        /// </summary>
        /// <param name="input"></param>
        /// <returns></returns>
        public res_AccountFeeSummary QueryAccountFeeSummary(req_AccountFee input)
        {
            var q = _Database.GetQueryable<dt_AccountFee>();
            var q_AccountItems = _Database.GetQueryable<dt_AccountItems>();

            q = q.Where(w => w.FlagApp == "Y");

            if (!input.FENO.IsEmpty())
                q = q.Where(w => w.FENO == input.FENO);

            if (input.DocDateFrom > Globals.MinSqlDate)
                q = q.Where(w => w.DocDate >= input.DocDateFrom);

            if (input.DocDateTo > Globals.MinSqlDate)
                q = q.Where(w => w.DocDate <= input.DocDateTo);

            if (!input.AccountId.IsEmpty())
                q = q.Where(w => w.AccountId == input.AccountId);

            if (!input.ARAP.IsEmpty())
                q = q.Where(w => w.ARAP == input.ARAP);

            if (!input.SONO.IsEmpty())
                q = q.Where(w => w.SONO == input.SONO);

            //左连接,left join
            var listSource = (from a in q
                              join b in q_AccountItems on a.AccountId equals b.ItemID into tmp
                              from b in tmp.DefaultIfEmpty()
                              select new
                              {
                                  isid = a.isid,
                                  YYYYMM = a.DocDate.Value.Year.ToString() + a.DocDate.Value.Month.ToString().PadLeft(2, '0'),
                                  ItemId = a.AccountId,
                                  ItemName = b != null ? b.ItemName : "",
                                  Amount = a.ARAP == "收" ? a.Amount : (a.Amount ?? 0) * -1,//收：正数，支：负数
                              }).ToList();

            //01/02/03项目编码
            var stringList = listSource.Select(s => s.ItemId).Distinct().ToList();

            //返回的结果数据
            var listResult = new List<res_AccountFeeSummaryItem>();

            //设置交叉表数据
            foreach (var item in listSource)
            {
                var row = listResult.Where(s => s.YYYYMM == item.YYYYMM).FirstOrDefault();

                if (row == null)
                {
                    row = new res_AccountFeeSummaryItem
                    {
                        YYYYMM = item.YYYYMM,
                        ItemId = item.ItemId,
                        ItemName = item.ItemName,
                    };
                    listResult.Add(row);
                }

                //生成属性名称：F01/F02/F03
                var fieldName = "F" + (stringList.IndexOf(item.ItemId) + 1).ToString().PadLeft(2, '0');

                //动态赋值
                ObjectHelper.SetPropertyValue(row, fieldName, (row.Amount ?? 0) + (item.Amount ?? 0));
            }

            //返回结果
            return new res_AccountFeeSummary
            {
                AccountItems = stringList,
                ListData = listResult,
            };
        }