Как реализовать цикл while в тесте Selenium с #

Store the value of the item in a variable before starting the loop and creata a variable with initial value int i =1 and with every time loop runs increment the value by and multiply it by the original value and match is with the value with you fetch from the UI eveytime..
int i = 1
while(condition){
i++
//price for each iteration `enter code here`
i*price for 1 item = "value from the UI"
}

Код ниже можно добавить в то место, где вы прокомментировали // I believe the while loop should be implemented here

String price = webDriver.FindElement(By.XPath("//span[@class='bag-item-price bag-item-price--current']"))
            .getAttribute("innerHTML");
int pricePerUnit = (int) Double.Parse(price.substring(1, price.Length - 1));
int qty = 1;
while (pricePerUnit * qty <= 200) {
    qty++;
}
qty--;
IWebElement quantityDropDown = webDriver.FindElement(
        By.XPath("//select[@class='bag-item-quantity bag-item-selector select2-hidden-accessible']"));
SelectElementFromDropDown(quantityDropDown, qty.ToString());

Вы можете реализовать свой сценарий без использования циклов (цикл for / while). Я добавил логику ниже. Отрисовка некоторых элементов занимает больше времени. Итак, я бы посоветовал добавить явное условие везде, где это необходимо.

Пожалуйста, найдите обновленный код и ознакомьтесь со всеми комментариями для получения более подробной информации.

Основной метод:

            IWebDriver webDriver = new ChromeDriver();
            webDriver.Navigate().GoToUrl("http://www.asos.com/men/");
            webDriver.Manage().Window.Maximize();
            webDriver.FindElement(By.XPath(".//input[@data-testid='search-input']")).SendKeys("nike trainers");
            webDriver.FindElement(By.XPath(".//button[@data-testid='search-button-inline']")).Click();

            //Search Result rendering will take some times.So, Explicit wait is mandatory
            WebDriverWait wait = new WebDriverWait(webDriver, TimeSpan.FromSeconds(5));
            IWebElement country = wait.Until(ExpectedConditions.ElementExists(By.CssSelector("article img")));
            webDriver.FindElement(By.CssSelector("article img")).Click();

            IWebElement Size = webDriver.FindElement(By.XPath(".//select[@data-id='sizeSelect']"));
            SelectElementFromDropDown(Size, "UK 10 - EU 45 - US 11");

            webDriver.FindElement(By.XPath("//*[@data-bind='text: buttonText']")).Click();

            //Add to cart takes some time.So, the below condition is needed 
            wait.Until(ExpectedConditions.ElementExists(By.XPath("//span[text()='Added']")));

            webDriver.FindElement(By.XPath("//a[@data-testid='bagIcon']")).Click();
            //Wait condition is needed after the page load
            //wait.Until(ExpectedConditions.TitleContains("Shopping"));

            wait.Until(ExpectedConditions.ElementExists(By.XPath("//select[contains(@class,'bag-item-quantity')]")));
            //Extract the price from the cart
            string totalPrice =webDriver.FindElement(By.XPath("//span[@class='bag-subtotal-price']")).Text;
            //Extract the price amount by exluding the currency
            double pricePerItem = Convert.ToDouble(totalPrice.Substring(1));

            // Just hardcoded the expected price limit value
            int priceLimit = 200;

            double noOfQuantity = priceLimit / pricePerItem;

            IWebElement qty =webDriver.FindElement(By.XPath("//select[contains(@class,'bag-item-quantity')]"));
            //Quantity values are rounded off with nearest lowest value . Example, 5.55 will be considered as 5 quantity
            SelectElementFromDropDown(qty, Math.Floor(noOfQuantity).ToString());

            //After updating the quantity, update  button will be displayed dynamically.So, wait is added and then update action is performed
            wait.Until(ExpectedConditions.ElementExists(By.XPath("//button[@class='bag-item-edit-update']")));
            webDriver.FindElement(By.XPath("//button[@class='bag-item-edit-update']")).Click();

Альтернативный подход с использованием цикла:

Я настоятельно рекомендую использовать описанный выше подход. поскольку количество будет увеличиваться один за другим каждый раз, пока предел цены не превысит 200

        //Extract the price from the cart
        string totalPrice = webDriver.FindElement(By.XPath("//span[@class='bag-subtotal-price']")).Text;
        double currentTotalPrice = Convert.ToDouble(totalPrice.Substring(1));
        double itemPerPrice = currentTotalPrice;

        // Just hardcoded the expected price limit value
        int priceLimit = 200;
        int quantity = 1;

        while(currentTotalPrice < priceLimit && priceLimit-currentTotalPrice > itemPerPrice)
        {
            wait.Until(ExpectedConditions.ElementExists(By.XPath("//select[contains(@class,'bag-item-quantity')]")));
            IWebElement qty = webDriver.FindElement(By.XPath("//select[contains(@class,'bag-item-quantity')]"));
            //Quantity values are rounded off with nearest lowest value . Example, 5.55 will be considered as 5 quantity
            SelectElementFromDropDown(qty, (++quantity).ToString());
            //After updating the quantity, update  button will be displayed dynamically.So, wait is added and then update action is performed
            wait.Until(ExpectedConditions.ElementExists(By.XPath("//button[@class='bag-item-edit-update']")));
            webDriver.FindElement(By.XPath("//button[@class='bag-item-edit-update']")).Click();

            wait.Until(ExpectedConditions.ElementExists(By.XPath("//span[@class='bag-subtotal-price']")));
            var temp = webDriver.FindElement(By.XPath("//span[@class='bag-subtotal-price']")).Text;

            currentTotalPrice = Convert.ToDouble(temp.Substring(1));
            Console.WriteLine("Current Price :" + currentTotalPrice);
        }