C#＋SeleniumでStaleElementReferenceError

Question

C#でSeleniumを使用して自動化処理を書いています。
(ブラウザはChromeです。)

OS: Windows10
IDE: Visual Studio 2015
Selenium: 3.11.2
ChromeDriver: 2.37.0

必ずではないのですが、頻繁に「stale element reference: element is not attached to the page document」という
StaleElementReferenceErrorが発生して困っています。

例えば、特定のaタグをクリックする処理で、DisplayedもtrueでTextの値も取れる状態でClickすると発生したりします。

色々調べたのですが、完全に描画されるまで待つしかなさそうで
以下のようにWebDriverWaitで待ってみたりしても不安定です…

        private static IWebElement FindElementEx(By by, uint timeOutInSeconds)
        {
            if (timeOutInSeconds > 0)
            {
                var wait = new WebDriverWait(webDriver, TimeSpan.FromSeconds(timeOutInSeconds));
                return wait.Until<IWebElement>(ctx => ctx.FindElement(by));
            }
            return webDriver.FindElement(by);
        }

仕方なく上の処理で要素を取得して、Sleep(1000)などとして回避していますが
もっとスマートなやり方はございませんでしょうか。

知っている方がいらっしゃればご教示お願いいたします。

Answer 1

stack over flowにそれっぽいのがあったので一先ず解決にします。
(これでもダメなときはダメですがマシにはなりました。)
需要があるかは分かりませんが一応、共有しておきます。

以下の拡張クラスをプロジェクトに追加します。

        /// <summary>
        ///     Method that finds an element based on the search parameters within a specified timeout.
        /// </summary>
        /// <param name="context">The context where this is searched. Required for extension methods</param>
        /// <param name="by">The search parameters that are used to identify the element</param>
        /// <param name="timeOutInSeconds">The time that the tool should wait before throwing an exception</param>
        /// <returns> The first element found that matches the condition specified</returns>
        public static IWebElement FindElement(this ISearchContext context, By by, uint timeOutInSeconds)
        {
            if (timeOutInSeconds > 0)
            {
                var wait = new DefaultWait<ISearchContext>(context);
                wait.Timeout = TimeSpan.FromSeconds(timeOutInSeconds);
                return wait.Until<IWebElement>(ctx => ctx.FindElement(by));
            }
            return context.FindElement(by);
        }
        /// <summary>
        ///     Method that finds a list of elements based on the search parameters within a specified timeout.
        /// </summary>
        /// <param name="context">The context where this is searched. Required for extension methods</param>
        /// <param name="by">The search parameters that are used to identify the element</param>
        /// <param name="timeoutInSeconds">The time that the tool should wait before throwing an exception</param>
        /// <returns>A list of all the web elements that match the condition specified</returns>
        public static IReadOnlyCollection<IWebElement> FindElements(this ISearchContext context, By by, uint timeoutInSeconds)
        {

            if (timeoutInSeconds > 0)
            {
                var wait = new DefaultWait<ISearchContext>(context);
                wait.Timeout = TimeSpan.FromSeconds(timeoutInSeconds);
                return wait.Until<IReadOnlyCollection<IWebElement>>(ctx => ctx.FindElements(by));
            }
            return context.FindElements(by);
        }
        /// <summary>
        ///     Method that finds a list of elements with the minimum amount specified based on the search parameters within a specified timeout.<br/>
        /// </summary>
        /// <param name="context">The context where this is searched. Required for extension methods</param>
        /// <param name="by">The search parameters that are used to identify the element</param>
        /// <param name="timeoutInSeconds">The time that the tool should wait before throwing an exception</param>
        /// <param name="minNumberOfElements">
        ///     The minimum number of elements that should meet the criteria before returning the list <para/>
        ///     If this number is not met, an exception will be thrown and no elements will be returned
        ///     even if some did meet the criteria
        /// </param>
        /// <returns>A list of all the web elements that match the condition specified</returns>
        public static IReadOnlyCollection<IWebElement> FindElements(this ISearchContext context, By by, uint timeoutInSeconds, int minNumberOfElements)
        {
            var wait = new DefaultWait<ISearchContext>(context);
            if (timeoutInSeconds > 0)
            {
                wait.Timeout = TimeSpan.FromSeconds(timeoutInSeconds);
            }

            // Wait until the current context found the minimum number of elements. If not found after timeout, an exception is thrown
            wait.Until<bool>(ctx => ctx.FindElements(by).Count >= minNumberOfElements);

            //If the elements were successfuly found, just return the list
            return context.FindElements(by);
        }

使い方は以下のような感じです。

ar driver = new FirefoxDriver();
driver.Navigate().GoToUrl("http://localhost");
var main = driver.FindElement(By.Id("main"));
// It can be now used to wait when using elements to search
var btn = main.FindElement(By.Id("button"),10);
btn.Click();
//This will wait up to 10 seconds until a button is found
var button = driver.FindElement(By.TagName("button"),10)
//This will wait up to 10 seconds until a button is found, and return all the buttons found
var buttonList = driver.FindElements(By.TagName("button"),10)
//This will wait for 10 seconds until we find at least 5 buttons
var buttonsMin= driver.FindElements(By.TagName("button"), 10, 5);
driver.Close();

色々やったのですが、上の対応を行いまだエラーが出る場合はSleepを少し入れるなどの対応で回避しています。
あまり試せていませんが、ボタンやリンクなどのクリックはJavaScriptでクリックするように仕込んだ方が安定するかもしれません。

C#でSelenium触ってる人は少ないんですかね…日本語の情報少ないです。