private void BtnSaveOrder_Click(object sender, RoutedEventArgs e) { if (customer != null) { if (selectedBooks.Any()) { if (MessageBox.Show("Do you want to add this order?", "Question", MessageBoxButton.YesNo, MessageBoxImage.Information) == MessageBoxResult.Yes) { Order order = new Order(); order.CustomerId = customer.Id; order.TakedDate = DateTime.Today; dr.AddOrder(order); RentedBook rentedBook = new RentedBook(); foreach (SelectedBook book in selectedBooks) { rentedBook.BookId = book.Id; rentedBook.OrderId = order.Id; rentedBook.ReturnDate = book.ReturnDate; rentedBook.CalcPrice = book.CalcPrice; rentedBook.Price = book.Price; dr.RentBook(book.Id); dr.AddRentBook(rentedBook); } } this.Close(); } else { MessageBox.Show("You not selected Book!!!"); } } else { MessageBox.Show("You not selected Customer!!!"); } }