Get a value of an attribute by XPath and HtmlAgilityPack

问题

I have a HTML document and I parse it with XPath. I want to get a value of the element input, but it didn't work.

My Html:

<tbody>
  <tr>
    <td>
      <input type="text" name="item" value="10743" readonly="readonly" size="10"/>
    </td>
  </tr>
</tbody>

My code:

using HtmlAgilityPack;

HtmlAgilityPack.HtmlDocument doc; 
HtmlWeb hw = new HtmlWeb();
HtmlNodeCollection node = doc.DocumentNode.SelectNodes("//input/@value");
string s=node[0].InnerText;

So I want to get the value: "10743" (and I don't mind to get another tags with the answer.)

回答1:

you can get it in .Attributes collection:

var doc = new HtmlAgilityPack.HtmlDocument();
doc.Load("file.html");
var node = doc.DocumentNode.SelectNodes("//input") [0];
var val = node.Attributes["value"].Value; //10743

回答2:

You can also directly grab the attribute if you use the HtmlNavigator.

//Load document from some html string
HtmlDocument hdoc = new HtmlDocument();
hdoc.LoadHtml(htmlContent);

//load navigator for current document
HtmlNavigator navigator = (HtmlNodeNavigator)hdoc.CreateNavigator();

//Get value with given xpath
string xpath = "//input/@value";
string val = navigator.SelectSingleNode(xpath).Value;

回答3:

Update2: Here is a code example how to get values of attributes using Html Agility Pack:

http://htmlagilitypack.codeplex.com/wikipage?title=Examples

 HtmlDocument doc = new HtmlDocument();
 doc.Load("file.htm");
 foreach(HtmlNode link in doc.DocumentElement.SelectNodes("//a[@href"])
 {
    HtmlAttribute att = link.Attributes["href"];
    att.Value = FixLink(att);
 }
 doc.Save("file.htm");

You obviously need to adapt this code to your needs -- for example you will not modify the attributes, but will just use att.Value .

Update: You may also look at this question:

Selecting attribute values with html Agility Pack

Your problem is most likely a default namespace problem -- search for "XPath default namespace c#" and you will find many good solutions (hint: use the overload of SelectNodes() that has an XmlNamespaceManager argument).

The following code shows what one gets for an attribute in a document in "no namespace":

using System;
using System.IO;
using System.Xml;

public class Sample
{

    public static void Main()
    {

        XmlDocument doc = new XmlDocument();
        doc.LoadXml("<input value='novel' ISBN='1-861001-57-5'>" +
                    "<title>Pride And Prejudice</title>" +
                    "</input>");

        XmlNode root = doc.DocumentElement;

        XmlNode value = doc.SelectNodes("//input/@value")[0];

        Console.WriteLine("Inner text: " + value.InnerText);
        Console.WriteLine("InnerXml: " + value.InnerXml);
        Console.WriteLine("OuterXml: " + value.OuterXml);
        Console.WriteLine("Value: " + value.Value);

    }
}

The result from running this app is:

Inner text: novel
InnerXml: novel
OuterXml: value="novel"
Value: novel

Now, for a document that is in a default namespace:

using System;
using System.IO;
using System.Xml;

public class Sample
{

    public static void Main()
    {

        XmlDocument doc = new XmlDocument();
        doc.LoadXml("<input xmlns='some:Namespace' value='novel' ISBN='1-861001-57-5'>" +
                    "<title>Pride And Prejudice</title>" +
                    "</input>");

        XmlNode root = doc.DocumentElement;

        XmlNamespaceManager nsmgr = new XmlNamespaceManager(doc.NameTable);
        nsmgr.AddNamespace("x", "some:Namespace");

        XmlNode value = doc.SelectNodes("//x:input/@value", nsmgr)[0];

        Console.WriteLine("Inner text: " + value.InnerText);
        Console.WriteLine("InnerXml: " + value.InnerXml);
        Console.WriteLine("OuterXml: " + value.OuterXml);
        Console.WriteLine("Value: " + value.Value);

    }
}

Running this app produces again the wanted results:

Inner text: novel
InnerXml: novel
OuterXml: value="novel"
Value: novel

来源：https://stackoverflow.com/questions/8666902/get-a-value-of-an-attribute-by-xpath-and-htmlagilitypack

标签

xpath

html-agility-pack