C# 解析具有 ajax 加载内容的网站

Question

如果我收到一个具有此功能的网站，我会得到整个页面，但没有 ajax 加载的值。

htmlDoc.LoadHtml(new WebClient().DownloadString(url));

是否可以像在 gChrome 中那样使用所有值加载网站？

Answer 1

不，在你的例子中是不可能的。因为它将以字符串形式加载内容。您应该在 "browser engine" 中呈现该字符串或找到任何可以为您完成该操作的组件。

我建议您查看 abotx 他们刚刚宣布了此功能，所以您可能会感兴趣，但它不是免费的。

Answer 2

您可以使用 WebBrowser control to get and render the page. Unfortunately, the control uses Internet Explorer and you have to change a registry value 来强制它使用最新版本，即使那样实现也非常脆弱。

另一种选择是采用独立的浏览器引擎，例如 WebKit and make it work in .NET. I found a page explaining how to do this, but it's pretty dated: http://webkitdotnet.sourceforge.net/basics.php

我开发了一个小演示应用程序来获取内容，这就是我想出的：

    class Program
    {
        static void Main(string[] args)
        {
            GetRenderedWebPage("https://siderite.dev", TimeSpan.FromSeconds(5), output =>
            {
                Console.Write(output);
                File.WriteAllText("output.txt", output);
            });
            Console.ReadKey();
        }

        private static void GetRenderedWebPage(string url, TimeSpan waitAfterPageLoad, Action<string> callBack)
        {
            const string cEndLine= "All output received";

            var sb = new StringBuilder();
            var p = new PhantomJS();
            p.OutputReceived += (sender, e) =>
            {
                if (e.Data==cEndLine)
                {
                    callBack(sb.ToString());
                } else
                {
                    sb.AppendLine(e.Data);
                }
            };
            p.RunScript(@"
var page = require('webpage').create();
page.viewportSize = { width: 1920, height: 1080 };
page.onLoadFinished = function(status) {
    if (status=='success') {
        setTimeout(function() {
            console.log(page.content);
            console.log('" + cEndLine + @"');
            phantom.exit();
        }," + waitAfterPageLoad.TotalMilliseconds + @");
    }
};
var url = '" + url + @"';
page.open(url);", new string[0]);
        }
    }

这使用 PhantomJS "headless" browser by way of the wrapper NReco.PhantomJS which you can get through "reference NuGet package" directly from Visual Studio. I am sure it can be done better, but this is what I did today. You might want to take a look at the PhantomJS callbacks so you can properly debug what is going on. My example will wait forever if the URL doesn't work, for example. Here is a useful link: https://newspaint.wordpress.com/2013/04/25/getting-to-the-bottom-of-why-a-phantomjs-page-load-fails/

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