提取HTML的正文类

//2、提取html的正文 类
using System;
 using System.Text;
 namespace HtmlStrip
 {
     class MainClass
     {
         public static void Main (string[] args)
         {
             string str = "<div>abc</div><span>efg</span><br /><script>888</script><!--<PA>WW</PA-->oo";
             //System.IO.StreamReader rd=new System.IO.StreamReader ("/home/lx/test.html");
             //str=rd.ReadToEnd ();
             HtmlParser t = new HtmlParser (str); //
             t.KeepTag (new string[] { "br" }); //设置br标签不过虑
             Console.Write (t.Text ());
         }
         
         
         
     }
     class HtmlParser
     {
         private string[] htmlcode; //把html转为数组形式用于分析
         private StringBuilder result = new StringBuilder ();  //输出的结果
         private int seek; //分析文本时候的指针位置
         private string[] keepTag;  //用于保存要保留的尖括号内容
         private bool _inTag;  //标记现在的指针是不是在尖括号内
         private bool needContent = true;  //是否要提取正文
         private string tagName;  //当前尖括号的名字
         private string[] specialTag = new string[] { "script", "style", "!--" };  //特殊的尖括号内容，一般这些标签的正文是不要的
         
         /// <summary>
         /// 当指针进入尖括号内，就会触发这个属性。这里主要逻辑是提取尖括号里的标签名字
         /// </summary>
         public bool inTag {
             get { return _inTag; }
             set {
                 _inTag = value;
                 if (!value)
                     return;
                 bool ok = true;
                 tagName = "";
                 while (ok) {
                     string word = read ();
                     if (word != " " && word != ">") {
                         tagName += word;
                     } else if (word == " " && tagName.Length > 0) {
                         ok = false;
                     } else if (word == ">") {
                         ok = false;
                         inTag = false;
                         seek -= 1;
                     }
                 }
             }
         }
         /// <summary>
         /// 初始化类
         /// </summary>
         /// <param name="html">
         ///  要分析的html代码
         /// </param>
         public HtmlParser (string html)
         {
             htmlcode = new string[html.Length];
             for (int i = 0; i < html.Length; i++) {
                 htmlcode[i] = html[i].ToString ();
             }
             KeepTag (new string[] {  });
         }
         /// <summary>
         /// 设置要保存那些标签不要被过滤掉
         /// </summary>
         /// <param name="tags">
         ///
         /// </param>
         public void KeepTag (string[] tags)
         {
             keepTag = tags;
         }
         
         /// <summary>
         /// 
         /// </summary>
         /// <returns>
         /// 输出处理后的文本
         /// </returns>
         public string Text ()
         {
             int startTag = 0;
             int endTag = 0;
             while (seek < htmlcode.Length) {
                 string word = read ();
                 if (word.ToLower () == "<") {
                     startTag = seek;
                     inTag = true;
                 } else if (word.ToLower () == ">") {
                     endTag = seek;
                     inTag = false;
                     if (iskeepTag (tagName.Replace ("/", ""))) {
                         for (int i = startTag - 1; i < endTag; i++) {
                             result.Append (htmlcode[i].ToString ());
                         }
                     } else if (tagName.StartsWith ("!--")) {
                         bool ok = true;
                         while (ok) {
                             if (read () == "-") {
                                 if (read () == "-") {
                                     if (read () == ">") {
                                         ok = false;
                                     } else {
                                         seek -= 1;
                                     }
                                 }
                             }
                         }
                     } else {
                         foreach (string str in specialTag) {
                             if (tagName == str) {
                                 needContent = false;
                                 break;
                             } else
                                 needContent = true;
                         }
                     }
                 } else if (!inTag && needContent) {
                     result.Append (word);
                 }
                 
             }
             return result.ToString ();
         }
         /// <summary>
         /// 判断是否要保存这个标签
         /// </summary>
         /// <param name="tag">
         /// A <see cref="System.String"/>
         /// </param>
         /// <returns>
         /// A <see cref="System.Boolean"/>
         /// </returns>
         private bool iskeepTag (string tag)
         {
             foreach (string ta in keepTag) {
                 if (tag.ToLower () == ta.ToLower ()) {
                     return true;
                 }
             }
             return false;
         }
         private string read ()
         {
             return htmlcode[seek++];
         }
 
     }
 }