public void Sell() { try { if (SelectedRecord != null) { SalesHistory s = new SalesHistory() { Date = Date, Record = SelectedRecord, SellingPrice = SelectedRecord.SellingPrice, DiscountPrice = total }; if (Client != null && Client.Name != "" && Client.Discount != null) { s.DiscountClient = (float)Client.Discount; s.ClientEmail = Client.Email; s.Client = Client; } if (Deal != null) { s.DiscountDeal = Deal.Discount; } if (Client != null && Client.Email == "") { s.ClientEmail = EmailClient; } DALService.SaleRecord(s); salesHistories.Add(s); if (Client != null && Client.Name != "") { Client.Discount = DALService.CalculateDiscount(Client); DALService.EditDiscountClient(Client, (float)Client.Discount); } OnPropertyChanged(nameof(Client)); Show(); } } catch (DbEntityValidationException ex) { foreach (DbEntityValidationResult validationError in ex.EntityValidationErrors) { MessageBox.Show(validationError.Entry.Entity.ToString()); foreach (DbValidationError err in validationError.ValidationErrors) { MessageBox.Show(err.ErrorMessage + ""); } } } catch (Exception ex1) { MessageBox.Show(ex1.Message); } }