How to extract the body of html and keep some content?

Text extraction is to remove the content in the html code. This code adds the option to retain certain content.

  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

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