public Prescription Create(Prescription model)
        {
            var dal = model.ToDAL();

            _db.Prescription.Add(dal);
            _db.SaveChanges();
            _db.SaveChanges();
            return(dal.ToBLL());
        }
        public bool Update(Prescription model)
        {
            var dal = model.ToDAL();

            var prescriptionMedicine = _db.PrescriptionMedicine.Where(pm => pm.PrescriptionId == model.Id).ToList();

            try
            {
                var pmIds          = dal.PrescriptionMedicine.Select(pm => pm.PrescriptionMedicineId).ToList();
                var persistenceIds = new List <int>();
                {
                    foreach (var pm in prescriptionMedicine)
                    {
                        if (pmIds.Contains(pm.PrescriptionMedicineId))
                        {
                            var dalPm = dal.PrescriptionMedicine.First(e => e.PrescriptionMedicineId == pm.PrescriptionMedicineId);
                            pm.MedicineId = dalPm.MedicineId;
                            pm.Amount     = dalPm.Amount;
                            //_db.PrescriptionMedicine.Update(pm);
                            persistenceIds.Add(pm.PrescriptionMedicineId);
                        }
                        else
                        {
                            _db.PrescriptionMedicine.Remove(pm);
                        }
                    }

                    _db.SaveChanges();
                }

                foreach (var medicine in dal.PrescriptionMedicine)
                {
                    if (!persistenceIds.Contains(medicine.PrescriptionMedicineId))
                    {
                        var newPm = new PrescriptionMedicine
                        {
                            Amount = medicine.Amount, MedicineId = medicine.MedicineId, PrescriptionId = medicine.PrescriptionId
                        };
                        _db.Add(newPm);
                        _db.SaveChanges();
                    }
                }
            }
            catch (Exception e)
            {
                return(false);
            }

            try
            {
                var updated = _db.Prescription
                              .First(e => e.PrescriptionId == dal.PrescriptionId);
                updated.Buyer    = dal.Buyer;
                updated.SaleTime = dal.SaleTime;
                updated.UserId   = dal.UserId;
                _db.Prescription.Update(updated);
                _db.SaveChanges();
                return(true);
            }
            catch
            {
                return(false);
            }
        }