public Reservation RedeemReservation(string serviceBrokerGuid, String userName,  
     String labServerGuid, string clientGuid)
 {
     UserSchedulingDB dbManager = new UserSchedulingDB();
     Coupon opCoupon = new Coupon();
     opCoupon.couponId = opHeader.coupon.couponId;
     opCoupon.passkey = opHeader.coupon.passkey;
     opCoupon.issuerGuid = opHeader.coupon.issuerGuid;
     string type = TicketTypes.REDEEM_RESERVATION;
     try
     {
         Ticket retrievedTicket = dbManager.RetrieveAndVerify(opCoupon, type);
         ReservationInfo res = dbManager.RedeemReservation(userName, serviceBrokerGuid, clientGuid, labServerGuid);
         if (res != null)
         {
             Reservation reservation = new Reservation(res.startTime, res.endTime);
             reservation.userName = res.userName;
             return reservation;
         }
         else
         {
             return null;
         }
     }
     catch
     {
         throw;
     }
 }