利用ASP.NET怎么對HTML字符串進行過濾

///  <summary>去除HTML標(biāo)記 
///     
///  </summary>   
///  <param name="Htmlstring">包括HTML的源碼</param>   
///  <returns>已經(jīng)去除后的文字</returns>   
public static string GetNoHTMLString(string Htmlstring) 
{ 
  //刪除腳本   
  Htmlstring = Regex.Replace(Htmlstring, @"<script[^>]*&#63;>.*&#63;</script>", "", RegexOptions.IgnoreCase); 
  //刪除HTML   
  Htmlstring = Regex.Replace(Htmlstring, @"<(.[^>]*)>", "", RegexOptions.IgnoreCase); 
  Htmlstring = Regex.Replace(Htmlstring, @"([\r\n])[\s]+", "", RegexOptions.IgnoreCase); 
  Htmlstring = Regex.Replace(Htmlstring, @"-->", "", RegexOptions.IgnoreCase); 
  Htmlstring = Regex.Replace(Htmlstring, @"<!--.*", "", RegexOptions.IgnoreCase); 

  Htmlstring = Regex.Replace(Htmlstring, @"&(quot|#34);", "\"", RegexOptions.IgnoreCase); 
  Htmlstring = Regex.Replace(Htmlstring, @"&(amp|#38);", "&", RegexOptions.IgnoreCase); 
  Htmlstring = Regex.Replace(Htmlstring, @"&(lt|#60);", "<", RegexOptions.IgnoreCase); 
  Htmlstring = Regex.Replace(Htmlstring, @"&(gt|#62);", ">", RegexOptions.IgnoreCase); 
  Htmlstring = Regex.Replace(Htmlstring, @"&(nbsp|#160);", "  ", RegexOptions.IgnoreCase); 
  Htmlstring = Regex.Replace(Htmlstring, @"&(iexcl|#161);", "\xa1", RegexOptions.IgnoreCase); 
  Htmlstring = Regex.Replace(Htmlstring, @"&(cent|#162);", "\xa2", RegexOptions.IgnoreCase); 
  Htmlstring = Regex.Replace(Htmlstring, @"&(pound|#163);", "\xa3", RegexOptions.IgnoreCase); 
  Htmlstring = Regex.Replace(Htmlstring, @"&(copy|#169);", "\xa9", RegexOptions.IgnoreCase); 
  Htmlstring = Regex.Replace(Htmlstring, @"&#(\d+);", "", RegexOptions.IgnoreCase); 

  Htmlstring.Replace("<", ""); 
  Htmlstring.Replace(">", ""); 
  Htmlstring.Replace("\r\n", ""); 
  Htmlstring = HttpContext.Current.Server.HtmlEncode(Htmlstring).Trim(); 

  return Htmlstring; 
} 

/// <summary>獲取顯示的字符串，可顯示HTML標(biāo)簽，但把危險的HTML標(biāo)簽過濾，如iframe,script等。 
///  
/// </summary> 
/// <param name="str">未處理的字符串</param> 
/// <returns></returns> 
public static string GetSafeHTMLString(string str) 
{ 
  str = Regex.Replace(str, @"<applet[^>]*&#63;>.*&#63;</applet>", "", RegexOptions.IgnoreCase); 
  str = Regex.Replace(str, @"<body[^>]*&#63;>.*&#63;</body>", "", RegexOptions.IgnoreCase); 
  str = Regex.Replace(str, @"<embed[^>]*&#63;>.*&#63;</embed>", "", RegexOptions.IgnoreCase); 
  str = Regex.Replace(str, @"<frame[^>]*&#63;>.*&#63;</frame>", "", RegexOptions.IgnoreCase); 
  str = Regex.Replace(str, @"<script[^>]*&#63;>.*&#63;</script>", "", RegexOptions.IgnoreCase); 
  str = Regex.Replace(str, @"<frameset[^>]*&#63;>.*&#63;</frameset>", "", RegexOptions.IgnoreCase); 
  str = Regex.Replace(str, @"<html[^>]*&#63;>.*&#63;</html>", "", RegexOptions.IgnoreCase); 
  str = Regex.Replace(str, @"<iframe[^>]*&#63;>.*&#63;</iframe>", "", RegexOptions.IgnoreCase); 
  str = Regex.Replace(str, @"<style[^>]*&#63;>.*&#63;</style>", "", RegexOptions.IgnoreCase); 
  str = Regex.Replace(str, @"<layer[^>]*&#63;>.*&#63;</layer>", "", RegexOptions.IgnoreCase); 
  str = Regex.Replace(str, @"<link[^>]*&#63;>.*&#63;</link>", "", RegexOptions.IgnoreCase); 
  str = Regex.Replace(str, @"<ilayer[^>]*&#63;>.*&#63;</ilayer>", "", RegexOptions.IgnoreCase); 
  str = Regex.Replace(str, @"<meta[^>]*&#63;>.*&#63;</meta>", "", RegexOptions.IgnoreCase); 
  str = Regex.Replace(str, @"<object[^>]*&#63;>.*&#63;</object>", "", RegexOptions.IgnoreCase); 
  return str; 
}