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++];
}

}
}