private void button1_Click(object sender, EventArgs e) { CashRegister_DAO cash = new CashRegister_DAO(); if (comboBoxCashRegister != null && comboBoxDrinks != null) { cash.CashAdder(comboBoxCashRegister.Text, comboBoxDrinks.Text); } comboBoxCashRegister.ResetText(); comboBoxDrinks.ResetText(); }