public IEnumerable <Reservation> GetUpcomingReservations(ReservationQuery query)
 {
     if (query.DateRange.DateFrom >= DateTime.Now)
     {
         throw new ArgumentNullException("dateFrom");
     }
     if (query.DateRange.DateTo <= DateTime.Now)
     {
         throw new ArgumentNullException("dateTo");
     }
     throw new NotImplementedException();
 }
        public IEnumerable <Reservation> GetReservations(ReservationQuery reservationQuery, int?customerId = null)
        {
            if (reservationQuery._dateRange.DateFrom >= DateTime.Now)
            {
                throw new ArgumentNullException("dateFrom");
            }
            if (reservationQuery._dateRange.DateTo <= DateTime.Now)
            {
                throw new ArgumentNullException("dateTo");
            }

            throw new NotImplementedException();
        }