asp.net替换和恢复html特殊字符

/// <summary>
/// 替换html中的特殊字符
/// </summary>
/// <param name="theString">需要进行替换的文本。</param>
/// <returns>替换完的文本。</returns>
public string HtmlEncode(string theString)
{
     theString=theString.Replace(">", "&gt;");
     theString=theString.Replace("<", "&lt;");
     theString=theString.Replace("  ", " &nbsp;");
     theString=theString.Replace("  ", " &nbsp;");
     theString=theString.Replace("\"", "&quot;");
     theString=theString.Replace("\'", "&#39;");
     theString=theString.Replace("\n", "<br/> ");
     return theString;
}

/// <summary>
/// 恢复html中的特殊字符
/// </summary>
/// <param name="theString">需要恢复的文本。</param>
/// <returns>恢复好的文本。</returns>
public string HtmlDiscode(string theString)
{
     theString=theString.Replace("&gt;", ">");
     theString=theString.Replace("&lt;", "<");
     theString=theString.Replace("&nbsp;"," ");
     theString=theString.Replace(" &nbsp;","  ");
     theString=theString.Replace("&quot;","\"");
     theString=theString.Replace("&#39;","\'");
     theString=theString.Replace("<br/> ","\n");
     return theString;
}