public List <Invitee> GetInvitees()
        {
            int reservationId = Reservation == null ? 0 : Reservation.ReservationID;
            int resourceId    = Reservation == null ? Resource.ResourceID : Reservation.ResourceID;

            List <Invitee> result;

            if (Helper.Context.Session[$"ReservationInvitees#{resourceId}"] == null)
            {
                result = ReservationInvitees.Create(Helper.Provider).SelectInvitees(reservationId);
                Helper.Context.Session[$"ReservationInvitees#{resourceId}"] = result;
            }
            else
            {
                result = (List <Invitee>)Helper.Context.Session[$"ReservationInvitees#{resourceId}"];
            }

            return(result);
        }
        public List <AvailableInvitee> GetAvailableInvitees()
        {
            int reservationId;
            int resourceId;
            int clientId;
            int activityId;

            if (Reservation != null)
            {
                reservationId = Reservation.ReservationID;
                resourceId    = Reservation.ResourceID;
                clientId      = Reservation.ClientID;
                activityId    = Reservation.ActivityID;
            }
            else
            {
                reservationId = 0;
                resourceId    = Resource.ResourceID;
                clientId      = CurrentUser.ClientID;
                activityId    = ActivityID;
            }

            List <AvailableInvitee> result;

            if (Helper.Context.Session[$"AvailableInvitees#{resourceId}"] == null)
            {
                result = ReservationInvitees.Create(Helper.Provider).SelectAvailable(reservationId, resourceId, activityId, clientId);
                Helper.Context.Session[$"AvailableInvitees#{resourceId}"] = result;
            }
            else
            {
                result = (List <AvailableInvitee>)Helper.Context.Session[$"AvailableInvitees#{resourceId}"];
            }

            return(result);
        }