为什么HTML敏捷性包HtmlDocument.DocumentNode为空？ [英] why HTML Agility Pack HtmlDocument.DocumentNode is null?

问题描述

我使用这个code更改HTML流的href属性。

I'm using this code to change the href attribute of a HTML stream.

首先，我下载使用这个code完整的HTML网页（网址为网页地址）

first I download a full html page using this code:(URL is webpage address)

HttpWebRequest myHttpWebRequest = (HttpWebRequest)WebRequest.Create(URL);
HttpWebResponse myHttpWebResponse = 
                         (HttpWebResponse)myHttpWebRequest.GetResponse();

Stream s = myHttpWebResponse.GetResponseStream();

然后我处理这个：

then I process this:

HtmlDocument doc = new HtmlDocument();

doc.Load(s);
foreach (HtmlNode link in doc.DocumentNode.SelectNodes("/a"))
{
    string att = link.Attributes["href"].Value;
    link.Attributes["href"].Value = "http://ahmadalli.somee.com/default.aspx?url=" + att;
}
doc.Save(s);

取值是HTML流。

但我有一个例外，说 doc.DocumentNode 为空！

but I've got an exception that says doc.DocumentNode is null!

我试过很多网站，但 doc.DocumentNode 为NULL

i tried many sites but doc.DocumentNode is null to

推荐答案

这为我工作。

using(WebClient client = new WebClient())
{
    client.Encoding = System.Text.Encoding.UTF8;
    var doc = new HtmlAgilityPack.HtmlDocument();
    doc.LoadHtml(client.DownloadString("http://www.google.com?q=stackoverflow"));
    foreach (var href in doc.DocumentNode.Descendants("a").Select(x => x.Attributes["href"]))
    {
        if (href == null) continue;
        href.Value = "http://ahmadalli.somee.com/default.aspx?url=" + HttpUtility.UrlEncode(href.Value);
    }
    StringWriter writer = new StringWriter();
    doc.Save(writer);
    var finalHtml = writer.ToString();
}

另请参阅 HttpUtility.UrlEn code 才能够回到正确获得url。否则，原始地址某些参数可能会引起问题。

Also see the HttpUtility.UrlEncode to be able to get the url back correctly. Otherwise, some parameters in original url may cause problem.

使用 HttpUtility.UrlDe code 脱code吧。

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