public TransactionForm()
        {
            InitializeComponent();
            con = new SqlConnection();
            con.ConnectionString = "Data Source=(localdb)\\MSSQLLocalDB;Initial Catalog=SQLdatabase;Integrated Security=True;Connect" +
                                   " Timeout=30;Encrypt=False;TrustServerCertificate=True;ApplicationIntent=ReadWrite;MultiSubnetFailover=False";
            dbc = new DBconnector();

            //get the first index
            int first = dbc.getFirstId("Transaction");

            //get the first transaction
            tr        = getTransactionFromDB(first);
            nId.Value = first;

            //get all transactions
            updateList();

            //show the first transaction
            fillForm();
        }