linq语句获取当天的数据

　　　　for (DateTime i = beforedate; i >= beforedate && i <= enddate; i = i.AddDays(1))
                {
                    var list = (from a in context.account
                                where a.deviceid == deviceid && EntityFunctions.DiffDays(a.tradetime, i) == 0
                                select a).ToList();
                    countList.Add(list.Count());
                }