HTML parsing Tool-htmlagility learning

Original: HTML parsing tool-htmlagility learning

Htmlagility is an open source HTML parsing library, which is said to be a C # version of jquery, very powerful.

This article learns its analytic function, can also simulate user request, create HTML, set up agent and so on, do not study.

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1. Simple examples

usingSystem;usingSystem.Collections.Generic;usingSystem.Linq;usingSystem.Text;usingSystem.Net;usingHtmlagilitypack;namespaceconsoleapplication1{classProgram {Static voidMain (string[] args) {Htmlweb webClient=NewHtmlweb (); HTMLDocument Doc= Webclient.load ("http://www.baidu.com"); varRootNode =Doc.            Documentnode; Htmlnodecollection categorynodelist= Rootnode.selectnodes ("//html[1]/body[1]"); foreach(varIteminchcategorynodelist) {Console.WriteLine ("Item:"+item.            Name);        } console.read (); }    }}

Is the first hellow world, grilled Baidu page.

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2. Read

Well, if it is loaded with local HTML or a direct read stream, the string. You can do this.

New htmldocument ();d OC. Load (@ "D:\xxx.mht"false);

 Public void Loadhtml (string html); // Direct-read-string-typed HTML  Public void Load (Stream stream); // Flow  Public void Load (string path); // Local Path

The htmldocumen itself also provides a method for detecting the encoding.

Htmlweb is mainly automatic detection of the code, if you want to customize the encoding can change the properties. Overrideencoding, autodetectencoding. And HTMLDocument on the operation of the code is not the same, specified in the parameters, it is estimated that the automatic detection of the code has been very powerful, very little to specify ....

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3. Node selection

RootNode.SelectNodesrootNode.SelectSingleNode

Select a node and select a single node.

Take selectnodes as an example and look at the parameters

Rootnode.selectnodes ("//html[1]/body[1]");

"//" double slash means finding all child nodes from the root node

The "/" slash indicates that only the first-level child node is found

The "./" dot slash indicates a lookup starting from the current node

[] A child node index in brackets that represents the same name.

var resultlist = Rootnode.selectnodes ("//html[1]/body[1]/div[1]/div[position () <5] "); // take the first 4 elements resultlist = Rootnode.selectnodes ("//html[1]/body[1]/div[1]/div[last ()]" ); // take the last 1 elements resultlist = Rootnode.selectnodes ("//html[1]/body[1]/div[1]/div[@id] "); // take all elements with an id attribute resultlist = rootnode.selectnodes ("//html[1]/body[1]/div[1]/div[@id = ' head ' ]"); // take an element with a property ID value of head

More properties can be viewed in W3school http://www.w3school.com.cn/xpath/xpath_functions.asp

Take attribute

Doc. attributes["ID"];

Take elements

Doc. getElementById ("ID");