C#解析HTML
在搜索引擎的开发中，我们需要对网页的Html内容进行检索，难免的就需要对Html进行解析。拆分每一个节点并且获取节点间的内容。此文介绍两种C#解析Html的方法。 第一种方法： 用System.Net.WebClient下载Web Page存到本地文件或者String中，用正则表达式来分析。这个方法可以用在Web Crawler等需要分析很多Web Page的应用中。 估计这也是大家最直接，最容易想到的一个方法。 转自网上的一个实例：所有的href都抽取出来：
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Code using System; using System.Net; using System.Text; using System.Text.RegularExpressions; namespace HttpGet { class Class1 { [STAThread] static void Main(string[] args) { System.Net.WebClient client = new WebClient(); byte[] page = client.DownloadData("http://www.google.com"); string content = System.Text.Encoding.UTF8.GetString(page); string regex = "href=[\\\"\\\'](http:\\/\\/|\\.\\/|\\/)?\\w+(\\.\\w+)*(\\/\\w+(\\.\\w+)?)*(\\/|\\?\\w*=\\w*(&\\w*=\\w*)*)?[\\\"\\\']"; Regex re = new Regex(regex); MatchCollection matches = re.Matches(content);
System.Collections.IEnumerator enu = matches.GetEnumerator(); while (enu.MoveNext() && enu.Current != null) { Match match = (Match)(enu.Current); Console.Write(match.Value + "\r\n"); } } } }
一些爬虫的HTML解析中也是用的类似的方法。 第二种方法：
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Code using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using Winista.Text.HtmlParser; using Winista.Text.HtmlParser.Lex; using Winista.Text.HtmlParser.Util; using Winista.Text.HtmlParser.Tags; using Winista.Text.HtmlParser.Filters;
namespace HTMLParser { public partial class Form1 : Form { public Form1() { InitializeComponent(); AddUrl(); }
private void btnParser_Click(object sender, EventArgs e) { #region 获得网页的html try {
txtHtmlWhole.Text = ""; string url = CBUrl.SelectedItem.ToString().Trim(); System.Net.WebClient aWebClient = new System.Net.WebClient(); aWebClient.Encoding = System.Text.Encoding.Default; string html = aWebClient.DownloadString(url); txtHtmlWhole.Text = html; } catch (Exception ex) { MessageBox.Show(ex.Message); } #endregion
#region 分析网页html节点 Lexer lexer = new Lexer(this.txtHtmlWhole.Text); Parser parser = new Parser(lexer); NodeList htmlNodes = parser.Parse(null); this.treeView1.Nodes.Clear(); this.treeView1.Nodes.Add("root"); TreeNode treeRoot = this.treeView1.Nodes[0]; for (int i = 0; i < htmlNodes.Count; i++) { this.RecursionHtmlNode(treeRoot, htmlNodes[i], false); }
#endregion
}
private void RecursionHtmlNode(TreeNode treeNode, INode htmlNode, bool siblingRequired) { if (htmlNode == null || treeNode == null) return;
TreeNode current = treeNode; TreeNode content ; //current node if (htmlNode is ITag) { ITag tag = (htmlNode as ITag); if (!tag.IsEndTag()) { string nodeString = tag.TagName; if (tag.Attributes != null && tag.Attributes.Count > 0) { if (tag.Attributes["ID"] != null) { nodeString = nodeString + " { id=\"" + tag.Attributes["ID"].ToString() + "\" }"; } if (tag.Attributes["HREF"] != null) { nodeString = nodeString + " { href=\"" + tag.Attributes["HREF"].ToString() + "\" }"; } } current = new TreeNode(nodeString); treeNode.Nodes.Add(current); } }
//获取节点间的内容 if (htmlNode.Children != null && htmlNode.Children.Count > 0) { this.RecursionHtmlNode(current, htmlNode.FirstChild, true); content = new TreeNode(htmlNode.FirstChild.GetText()); treeNode.Nodes.Add(content); }
//the sibling nodes if (siblingRequired) { INode sibling = htmlNode.NextSibling; while (sibling != null) { this.RecursionHtmlNode(treeNode, sibling, false); sibling = sibling.NextSibling; } } } private void AddUrl() { CBUrl.Items.Add("http://www.hao123.com"); CBUrl.Items.Add("http://www.sina.com"); CBUrl.Items.Add("http://www.heuet.edu.cn"); }
} }
Code using System; using System.Net; using System.Text; using System.Text.RegularExpressions; namespace HttpGet { class Class1 { [STAThread] static void Main(string[] args) { System.Net.WebClient client = new WebClient(); byte[] page = client.DownloadData("http://www.google.com"); string content = System.Text.Encoding.UTF8.GetString(page); string regex = "href=[\\\"\\\'](http:\\/\\/|\\.\\/|\\/)?\\w+(\\.\\w+)*(\\/\\w+(\\.\\w+)?)*(\\/|\\?\\w*=\\w*(&\\w*=\\w*)*)?[\\\"\\\']"; Regex re = new Regex(regex); MatchCollection matches = re.Matches(content);System.Collections.IEnumerator enu = matches.GetEnumerator(); while (enu.MoveNext() && enu.Current != null) { Match match = (Match)(enu.Current); Console.Write(match.Value + "\r\n"); } } } }
利用Winista.Htmlparser.Net 解析Html。这是.NET平台下解析Html的开源代码，网上有源码下载，百度一下就能搜到，这里就不提供了。并且有英文的帮助文档。找不到的留下邮箱。 个人认为这是.net平台下解析html不错的解决方案，基本上能够满足我们对html的解析工作。 自己做了个实例：
Code using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using Winista.Text.HtmlParser; using Winista.Text.HtmlParser.Lex; using Winista.Text.HtmlParser.Util; using Winista.Text.HtmlParser.Tags; using Winista.Text.HtmlParser.Filters;namespace HTMLParser { public partial class Form1 : Form { public Form1() { InitializeComponent(); AddUrl(); }
private void btnParser_Click(object sender, EventArgs e) { #region 获得网页的html try {
txtHtmlWhole.Text = ""; string url = CBUrl.SelectedItem.ToString().Trim(); System.Net.WebClient aWebClient = new System.Net.WebClient(); aWebClient.Encoding = System.Text.Encoding.Default; string html = aWebClient.DownloadString(url); txtHtmlWhole.Text = html; } catch (Exception ex) { MessageBox.Show(ex.Message); } #endregion
#region 分析网页html节点 Lexer lexer = new Lexer(this.txtHtmlWhole.Text); Parser parser = new Parser(lexer); NodeList htmlNodes = parser.Parse(null); this.treeView1.Nodes.Clear(); this.treeView1.Nodes.Add("root"); TreeNode treeRoot = this.treeView1.Nodes[0]; for (int i = 0; i < htmlNodes.Count; i++) { this.RecursionHtmlNode(treeRoot, htmlNodes[i], false); }
#endregion
}
private void RecursionHtmlNode(TreeNode treeNode, INode htmlNode, bool siblingRequired) { if (htmlNode == null || treeNode == null) return;
TreeNode current = treeNode; TreeNode content ; //current node if (htmlNode is ITag) { ITag tag = (htmlNode as ITag); if (!tag.IsEndTag()) { string nodeString = tag.TagName; if (tag.Attributes != null && tag.Attributes.Count > 0) { if (tag.Attributes["ID"] != null) { nodeString = nodeString + " { id=\"" + tag.Attributes["ID"].ToString() + "\" }"; } if (tag.Attributes["HREF"] != null) { nodeString = nodeString + " { href=\"" + tag.Attributes["HREF"].ToString() + "\" }"; } } current = new TreeNode(nodeString); treeNode.Nodes.Add(current); } }
//获取节点间的内容 if (htmlNode.Children != null && htmlNode.Children.Count > 0) { this.RecursionHtmlNode(current, htmlNode.FirstChild, true); content = new TreeNode(htmlNode.FirstChild.GetText()); treeNode.Nodes.Add(content); }
//the sibling nodes if (siblingRequired) { INode sibling = htmlNode.NextSibling; while (sibling != null) { this.RecursionHtmlNode(treeNode, sibling, false); sibling = sibling.NextSibling; } } } private void AddUrl() { CBUrl.Items.Add("http://www.hao123.com"); CBUrl.Items.Add("http://www.sina.com"); CBUrl.Items.Add("http://www.heuet.edu.cn"); }
} }
运行效果：
实现取来很容易，结合Winista.Htmlparser源码很快就可以实现想要的效果。
小结： 简单介绍了两种解析Html的方法，大家有什么其他好的方法还望指教。
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