如何在Selenium C#中防止PageFactory中的StaleElementReection ceException？

Question

我在C#6中有一个Selenium WebDriver页面对象模型。在尝试单击ajax加载的导航栏元素时，我遇到了StaleElementReferenceException。这很混乱，因为我使用的是页面工厂，没有任何缓存查找。

这是有问题的代码。我试着把重要的部分简单化。（我实际上传递了一个驱动程序，一个包装器，包装了IWebDriver）<代码>菜单栏。选择英语

public class Tests
{
    [Test]
    public void SelectEnglishTest()
    {
        homePage
            .MenuBar.SelectEnglish<HomePage>();
    }

    // ...
}

public class MenuBar : PageObject
{
    [FindsBy(How = How.CssSelector, Using = "...")]
    private IWebElement Language { get; set; }

    [FindsBy(How = How.CssSelector, Using = "...")]
    private IWebElement English { get; set; }

    public T SelectEnglish<T>() where T : Page
    {
        Language.Click();
        IWait<IWebDriver> wait = new WebDriverWait(Driver, TimeSpan.FromSeconds(5));
        wait.Until(ExpectedConditions.ElementToBeClickable(English));
        English.Click();
        Thread.CurrentThread.CurrentUICulture = CultureInfo.GetCultureInfo("en-US");
        return (T)Activator.CreateInstance(typeof(T), Driver);
    }

    // ...
}

public class HomePage : PageObject
{
    public MenuBar MenuBar { get; private set; }

    // ...
}

public class PageObject
{
    protected IWebDriver Driver { get; }

    protected PageObject(IWebDriver driver)
    {
        Driver = driver;
        PageFactory.InitElements(this, new RetryingElementLocator(Driver, TimeSpan.FromSeconds(20)));
    }

    // ...
}

导致此错误的原因是什么？我该怎么办？

Answer 1

从文档中，陈旧元素引用异常

A stale element reference exception is thrown in one of two cases, the first being more common than the second:
 - The element has been deleted entirely.
 - The element is no longer attached to the DOM.

由于您提到元素是使用Ajax加载的，因此很可能是在页面对象获取元素后该元素发生了更改。只需再次获取它，或者等待Ajax完成，然后再获取受影响的元素。

编辑1

下面是一些示例代码，演示如何在使用PageFactory的同时使用方法获取元素。

using OpenQA.Selenium;
using OpenQA.Selenium.Firefox;
using OpenQA.Selenium.Support.PageObjects;
using System;

namespace C_Sharp_Selenium_Test
{
    class Program
    {
        static void Main(string[] args)
        {
            FirefoxDriver driver = new FirefoxDriver();
            driver.Navigate().GoToUrl("http://www.google.com");
            HomePage homePage = new HomePage(driver);
            PageFactory.InitElements(driver, homePage);
            homePage.search("stack overflow");
            homePage.getSearchBox().Clear();
            homePage.getSearchBox().SendKeys("c# pagefactory");
            homePage.getSearchButton().Click();
        }
    }

    public class HomePage
    {
        private By searchBox = By.Id("lst-ib");
        private By searchButton = By.Name("btnG");

        // add other elements in here that use FindsBy() to be loaded using PageFactory.InitElements()

        private IWebDriver driver;

        public void search(String s)
        {
            getSearchBox().SendKeys(s);
            getSearchButton().Click();
        }

        public IWebElement getSearchBox()
        {
            return driver.FindElement(searchBox);
        }

        public IWebElement getSearchButton()
        {
            return driver.FindElement(searchButton);
        }

        public HomePage(IWebDriver driver)
        {
            this.driver = driver;
        }
    }
}