using HtmlAgilityPack for parsing a web page information in C#

问题

I'm trying to use HtmlAgilityPack for parsing a web page information. This is my code:

using System;
using HtmlAgilityPack;

namespace htmparsing
{
    class MainClass
    {
        public static void Main (string[] args)
        {
            string url = "https://bugs.eclipse.org";
            HtmlWeb web = new HtmlWeb();
            HtmlDocument doc = web.Load(url);
            foreach(HtmlNode node in doc){
                //do something here with "node"
            }               
        }
    }
}

But when I tried to access to doc.DocumentElement.SelectNodes I can not see DocumentElement in the list. I added the HtmlAgilityPack.dll in the references, but I don't know what's the problem.

回答1:

I've an article that demonstrates scraping DOM elements with HAP (HTML Agility Pack) using ASP.NET. It simply lets you go through the whole process step by step. You can have a look and try it.

Scraping HTML DOM elements using HtmlAgilityPack (HAP) in ASP.NET

and about your process it's working fine for me. I've tried this way as you did with a single change.

string url = "https://www.google.com";
HtmlWeb web = new HtmlWeb();
HtmlDocument doc = web.Load(url);
foreach (HtmlNode node in doc.DocumentNode.SelectNodes("//a")) 
{
    outputLabel.Text += node.InnerHtml;
}

Got the output as expected. The problem is you are asking for DocumentElement from HtmlDocument object which actually should be DocumentNode. Here's a response from a developer of HTMLAgilityPack about the problem you are facing.

HTMLDocument.DocumentElement not in object browser

回答2:

The behavior you are seeing is correct.

Look at what you're actually doing: http://htmlagilitypack.codeplex.com/SourceControl/latest#Release/1_4_0/HtmlAgilityPack/HtmlNode.cs .

You're asking the top element to select nodes matching some xpath. Unless your xpath expression starts with a //, you're asking it for relative nodes, which are descendant nodes. A document element is a not a descendant of itself, because no element is a descendant of itself.

来源：https://stackoverflow.com/questions/19870116/using-htmlagilitypack-for-parsing-a-web-page-information-in-c-sharp

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