public void UpdateProductQuantity(int productNumber, int newQuantity) { if (productNumber > QuantityBoxes.Count()) { throw new ArgumentException("There are less added items in the cart. Please specify smaller product number."); } var browserService = new BrowserService(); browserService.WaitUntilReady(); QuantityBoxes[productNumber - 1].SetNumber(newQuantity); UpdateCart.Click(); browserService.WaitUntilReady(); }