asp.net过滤HTML标签，只保留换行与空格

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自己从网上找了一个过滤HTML标签的方法，我也不知道谁的才是原创的，反正很多都一样。我把那方法复制下来，代码如下：

///   <summary>

///   去除HTML标记

///   </summary>

///   <param   name="NoHTML">包括HTML的源码   </param>

///   <returns>已经去除后的文字</returns>

public static string NoHTML(string Htmlstring)

{

  //删除脚本

  Htmlstring = Regex.Replace(Htmlstring, @"<script[^>]*?>.*?</script>", "",

    RegexOptions.IgnoreCase);

  //删除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;

}

以上代码是从网上直接复制过来的，这个确实能过滤掉所有的HTML标签，但是这个不是我想要的，这个过滤得太干净了，我如果用textarea输入框的话，我是要保留空格跟换行的。

然后我就自己改了一下这个方法，textarea的换行是\n，所以我得把这些标签重新匹配替换成<br>，这样的话从数据库中读取到页面时，就能正确的换行了，把空格替换成HTML的空格符，大功告成。

       ///   <summary>

        ///   去除HTML标记(保留br跟\r\n)（此方法由博客园-三卷天书修改成）

        ///   </summary>

        ///   <param   name="NoHTML">包括HTML的源码   </param>

        ///   <returns>已经去除后的文字</returns>

        public static string NewNoHTML(string Htmlstring)

        {

            //Htmlstring.Replace("\\r\\n", "%r%n").Replace("<br>","%br%").Replace("<br/>","%br&%").Replace("\\n","%n");

            //删除脚本

            Htmlstring = Regex.Replace(Htmlstring, @"<script[^>]*?>.*?</script>", "",

              RegexOptions.IgnoreCase);

            //删除HTML

            Htmlstring = Regex.Replace(Htmlstring, @"<(.[^>]*)>", "",

              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);

            Htmlstring = Regex.Replace(Htmlstring, @"((\r\n))", "<br>");

            Htmlstring = Regex.Replace(Htmlstring, @"(\r|\n)", "<br>");

            Htmlstring = Regex.Replace(Htmlstring, @"(\s)", "&nbsp;");

            return Htmlstring;

        }