public List <Bill> GetBillsByCusID(string cusID) { List <Bill> listBills = null; listBills = BillDAL.GetBillsByCustomerID(cusID); for (int i = 0; i < listBills.Count(); i++) { for (int j = i + 1; j < listBills.Count(); j++) { if (listBills[i].Id().Equals(listBills[j].Id())) { listBills.Remove(listBills[j]); } } } return(listBills); }