如何擷取html的正文以及保留某些<>內容？

  1   using System;
  2 using System.Text;
   3 namespace HtmlStrip
  4 {
  5     class MainClass
  6     {
  7         public static void Main (string[] args)
  8         {
  9             string str = "<p>abc</p><span>efg</span><br /><script>888</script><!--<PA>WW</PA-->oo";
 10             //System.IO.StreamReader rd=new System.IO.StreamReader ("/home/lx/test.html");
 11             //str=rd.ReadToEnd ();
 12             HtmlParser t = new HtmlParser (str); //
 13             t.KeepTag (new string[] { "br" }); //设置br标签不过虑
 14             Console.Write (t.Text ());
 15         }
 16         
 17         
 18         
 19     }
 20     class HtmlParser
 21     {
 22         private string[] htmlcode; //把html转为数组形式用于分析
 23         private StringBuilder result = new StringBuilder ();  //输出的结果
 24         private int seek; //分析文本时候的指针位置
 25         private string[] keepTag;  //用于保存要保留的尖括号内容
 26         private bool _inTag;  //标记现在的指针是不是在尖括号内
 27         private bool needContent = true;  //是否要提取正文
 28         private string tagName;  //当前尖括号的名字
 29         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
 30         
 31         /// <summary>
 32         /// 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
 33         /// </summary>
 34         public bool inTag {
 35             get { return _inTag; }
 36             set {
 37                 _inTag = value;
 38                 if (!value)
 39                     return;
 40                 bool ok = true;
 41                 tagName = "";
 42                 while (ok) {
 43                     string word = read ();
 44                     if (word != " " && word != ">") {
 45                         tagName += word;
 46                     } else if (word == " " && tagName.Length > 0) {
 47                         ok = false;
 48                     } else if (word == ">") {
 49                         ok = false;
 50                         inTag = false;
 51                         seek -= 1;
 52                     }
 53                 }
 54             }
 55         }
 56         /// <summary>
 57         /// 初始化类
 58         /// </summary>
 59         /// <param name="html">
 60         ///  要分析的html代码
 61         /// </param>
 62         public HtmlParser (string html)
 63         {
 64             htmlcode = new string[html.Length];
 65             for (int i = 0; i < html.Length; i++) {
 66                 htmlcode[i] = html[i].ToString ();
 67             }
 68             KeepTag (new string[] {  });
 69         }
 70         /// <summary>
 71         /// 设置要保存那些标签不要被过滤掉
 72         /// </summary>
 73         /// <param name="tags">
 74         ///
 75         /// </param>
 76         public void KeepTag (string[] tags)
 77         {
 78             keepTag = tags;
 79         }
 80         
 81         /// <summary>
 82         /// 
 83         /// </summary>
 84         /// <returns>
 85         /// 输出处理后的文本
 86         /// </returns>
 87         public string Text ()
 88         {
 89             int startTag = 0;
 90             int endTag = 0;
 91             while (seek < htmlcode.Length) {
 92                 string word = read ();
 93                 if (word.ToLower () == "<") {
 94                     startTag = seek;
 95                     inTag = true;
 96                 } else if (word.ToLower () == ">") {
 97                     endTag = seek;
 98                     inTag = false;
 99                     if (iskeepTag (tagName.Replace ("/", ""))) {
100                         for (int i = startTag - 1; i < endTag; i++) {
101                             result.Append (htmlcode[i].ToString ());
102                         }
103                     } else if (tagName.StartsWith ("!--")) {
104                         bool ok = true;
105                         while (ok) {
106                             if (read () == "-") {
107                                 if (read () == "-") {
108                                     if (read () == ">") {
109                                         ok = false;
110                                     } else {
111                                         seek -= 1;
112                                     }
113                                 }
114                             }
115                         }
116                     } else {
117                         foreach (string str in specialTag) {
118                             if (tagName == str) {
119                                 needContent = false;
120                                 break;
121                             } else
122                                 needContent = true;
123                         }
124                     }
125                 } else if (!inTag && needContent) {
126                     result.Append (word);
127                 }
128                 
129             }
130             return result.ToString ();
131         }
132         /// <summary>
133         /// 判断是否要保存这个标签
134         /// </summary>
135         /// <param name="tag">
136         /// A <see cref="System.String"/>
137         /// </param>
138         /// <returns>
139         /// A <see cref="System.Boolean"/>
140         /// </returns>
141         private bool iskeepTag (string tag)
142         {
143             foreach (string ta in keepTag) {
144                 if (tag.ToLower () == ta.ToLower ()) {
145                     return true;
146                 }
147             }
148             return false;
149         }
150         private string read ()
151         {
152             return htmlcode[seek++];
153         }
154 
155     }
156 }
157