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(">", ">");
     thestring=thestring.replace("<", "<");
     thestring=thestring.replace("  ", "  ");
     thestring=thestring.replace("  ", "  ");
     thestring=thestring.replace("\"", """);
     thestring=thestring.replace("\'", "'");
     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(">", ">");
     thestring=thestring.replace("<", "<");
     thestring=thestring.replace(" "," ");
     thestring=thestring.replace("  ","  ");
     thestring=thestring.replace(""","\"");
     thestring=thestring.replace("'","\'");
     thestring=thestring.replace("<br/> ","\n");
     return thestring;
}