//return selected customer and his rented books private void CustomerSelected(object sender, EventArgs e) { lblBookPriceCount.Content = 0; lbldelayCount.Content = 0; lblOrderSummaryCount.Content = 0; dgCustomerReturnBook.Items.Clear(); returnRentedBookLists.Clear(); customer = sender as Customer; if (customer != null) { tbCustomerName.Text = customer.FullName; rentedBooks = dr.SearchRentedBook(customer.Id); this.dgCustomerTackedBook.Items.Clear(); foreach (ReturnRentedBookList book in rentedBooks) { this.dgCustomerTackedBook.Items.Add(book); } } }