private IEnumerable <Notification> GetReferralNotifications(int doctorId)
        {
            var notifications = new List <Notification>();

            IEnumerable <Referral> referrals = _referralRepository.GetReferralsForReferredDoctor(doctorId);

            foreach (Referral referral in referrals)
            {
                if (referral.SeenByReferredDoctor)
                {
                    continue;
                }

                Patient referralPatient = _patientRepository.GetPatient(referral.PatientId);
                Doctor  referringDoctor = _doctorRepository.GetDoctor(referral.ReferringDoctorId);

                string message = "Patient " + referralPatient.FirstName + " " +
                                 referralPatient.LastName + " has been referred to you by Dr. " +
                                 referringDoctor.LastName + ".";

                notifications.Add(new Notification
                {
                    NotificationId = referral.ReferralId,
                    Type           = NotificationType.Referral,
                    Message        = message,
                    PatientId      = referral.PatientId
                });
            }

            return(notifications);
        }