static public void Add_bills(string order_form) { if (bills == null) { bills = (new Bills_history(order_form)); } else { bills.Add_to_bill(order_form); } }
static public void Clear() { bills = null; }
static public void Add_bills(string order_form) { if (bills == null) { bills = (new Bills_history(order_form)); } else { bills.Add_to_bill(order_form); } }
static public void Clear() { bills = null; }