请教一个关于UBB编码转换的问题

以下是我写的ubb编码转换函数，但是发现只要数据大是，打开速度特别慢，尤其是当论坛回复的数据内容特别多，同时有用UBB标签时，打开速度将更慢，请问诸位有什么好的解决方案，提升速度呢？或者帮指出效率低下的原因：论坛地址为http://www.rfidworld.com.cn/bbs/Thread-b15.htm(这里有比较多的翻页数据)

 

ubb编码转换Begin#region ubb编码转换Begin
        /**//// <summary>
        /// ubb编码转换函数
        /// </summary>
        /// <param name="ubb">要转换的字符串</param>
        /// <returns></returns>
        public static string ConvertUBB(string ubb)
        {
            if (string.IsNullOrEmpty(ubb))
                return "";
            if (ubb.IndexOf("[") == -1 || ubb.IndexOf("]") == -1)
            {
                return DeUrlLink(ubb).Replace("\n", "<br />");
            }
            ubb = DeUrl(ubb);
            ubb = DeUpload(ubb);
            ubb = DeImg(ubb);
            ubb = DeUrlLink(ubb);
            ubb = DeColor(ubb);
            ubb = DeFont(ubb);
            ubb = DecodeBlank(ubb);
            return ubb;
        }

        /**//// <summary>
        /// 转换[URL]标签
        /// </summary>
        /// <param name="ubb">要转换的字符串</param>
        /// <returns></returns>
        private static string DeUrl(string ubb)
        {
            ubb = Regex.Replace(ubb, @"(\[URL\])(.[^\[]*)(\[\/URL\])"
                , "<a href=\"$2\" target=\"_blank\"><u><font color=blue>$2</font></u></a>", options);
            ubb = Regex.Replace(ubb, @"(\[URL=(.[^\[]*)\])(.[^\[]*)(\[\/URL\])"
                , "<a href=\"$2\" target=\"_blank\"><u><font color=blue>$3</font></u></a>", options);
            ubb = Regex.Replace(ubb, @"(\[URL\])(\[\/URL\])", "", options);
            ubb = Regex.Replace(ubb, @"(\[URL=(.[^\[]*)\])(\[\/URL\])", "", options);
            return ubb;
        }

        /**//// <summary>
        /// 转换[UPLOAD]标签
        /// </summary>
        /// <param name="ubb">要转换的字符串</param>
        /// <returns></returns>
        private static string DeUpload(string ubb)
        {
            ubb = Regex.Replace(ubb, @"\[UPLOAD=(.[^\[]*)\](.[^\[]*)\[\/UPLOAD\]"
                , "<br><a href=\"$1\" title=\"点击这里下载该文件\" TARGET=\"_blank\"><img src=\"Images/1.gif\"  border=\"0\" /><font color=#0000CC>$2</font></a>", options);
            ubb = Regex.Replace(ubb, @"\[UPLOAD=(.[^\[]*)\]\[\/UPLOAD\]"
                , "<br><a href=\"$1\" title=\"点击这里下载该文件\" TARGET=\"_blank\"><img src=\"Images/1.gif\"  border=\"0\" /><font color=#0000CC>下载</font></a>", options);
            ubb = Regex.Replace(ubb, @"\[UPLOAD=(.[^\[]*)\]\[\/UPLOAD\]", "", options);
            ubb = ubb.Replace("Download.asp?", "Download.aspx?");
            return ubb;
        }

        /**//// <summary>
        /// 转换[IMG]标签
        /// </summary>
        /// <param name="ubb">要转换的字符串</param>
        /// <returns></returns>
        private static string DeImg(string ubb)
        {
            ubb = Regex.Replace(ubb, @"\[IMG\](.[^\[]*)\[\/IMG\]", "<a href=\"$1\" TARGET=\"_blank\"><img src=\"$1\" border=\"0\" onload=\"javascript:if(this.width>600)this.style.width=600;\"></a>", options);
            ubb = Regex.Replace(ubb, @"\[IMG\]\[\/IMG\]", "", options);
            return ubb;
        }

        /**//// <summary>
        /// 对文章中的url进行超链接
        /// </summary>
        /// <param name="ubb">要转换的字符串</param>
        /// <returns></returns>
        private static string DeUrlLink(string ubb)
        {
            ubb = Regex.Replace(ubb, @"^((?:http|ftp|rtsp|mms)://((?!&nbsp;|&quot;|&apos;)[A-Za-z0-9\./=\?%\-&_~`@':+!])+)"
                , "<a target=\"_blank\" href=\"$1\"><font color=blue><u>$1</u></font></a>", options);
            ubb = Regex.Replace(ubb, @"([^>=""])((?:http|ftp|rtsp|mms)://((?!&nbsp;|&quot;|&apos;)[A-Za-z0-9\./=\?%\-&_~`@':+!])+)"
                , "$1<a target=\"_blank\" href=\"$2\"><font color=blue><u>$2</u></font></a>", options);
            ubb = Regex.Replace(ubb, @"^(www\.((?!&nbsp;|&quot;|&apos;)[A-Za-z0-9\./=\?%\-&_~`@':+!])+)"
                , "<a target=\"_blank\" href=\"http://$1\">$1</a>", options);
            ubb = Regex.Replace(ubb, @"([^A-Za-z>=/\.\\""])(www\.((?!&nbsp;|&quot;|&apos;)[A-Za-z0-9\./=\?%\-&_~`@':+!])+)"
                , "$1<a target=\"_blank\" href=\"http://$2\"><font color=blue><u>$2</u></font></a>", options);
            return ubb;
        }

        /**//// <summary>
        /// 转换[COLOR]标签
        /// </summary>
        /// <param name="ubb">要转换的字符串</param>
        /// <returns></returns>
        private static string DeColor(string ubb)
        {
            ubb = Regex.Replace(ubb, @"\[color=(.[^\[]*)\](.[^\[]*)\[\/color\]", "<span style=\"color:$1\">$2</span>", options);
            ubb = Regex.Replace(ubb, @"\[color=(.[^\[]*)\]\[\/color\]", "", options);
            return ubb;
        }

        /**//// <summary>
        /// 转换字体标签
        /// </summary>
        /// <param name="ubb">要转换的字符串</param>
        /// <returns></returns>
        private static string DeFont(string ubb)
        {
            ubb = Regex.Replace(ubb, @"\[i\](.[^\[]*)\[\/i\]", "<span style=\"font-style:italic\">$1</span>", options);
            ubb = Regex.Replace(ubb, @"\[i\]\[\/i\]", "", options);
            ubb = Regex.Replace(ubb, @"\[u\](.[^\[]*)\[\/u\]", "<span style=\"text-decoration:underline\">$1</span>", options);
            ubb = Regex.Replace(ubb, @"\[u\]\[\/u\]", "", options);
            ubb = Regex.Replace(ubb, @"\[b\](.[^\[]*)\[\/b\]", "<span style=\"font-weight:bold\">$1</span>", options);
            ubb = Regex.Replace(ubb, @"\[b\](\[\/b\])", "", options);
            ubb = Regex.Replace(ubb, @"\[b\]\[\/b\]", "", options);
            ubb = Regex.Replace(ubb, @"\[QUOTE\](.[^\[]*)\[\/QUOTE\]"
                , "<table style=\"width:100%\" cellpadding=5 cellspacing=1><TR><TD style='border-right: #cccccc 1px solid; border-top:#cccccc 1px solid; border-left: #cccccc 1px solid; border-bottom: #cccccc 1px solid;background-color:#f6f6f6' width=\"100%\">$1</td></tr></table>", options);
            ubb = Regex.Replace(ubb, @"\[QUOTE\]\[\/QUOTE\]", "", options);
            ubb = Regex.Replace(ubb, @"\[EDIT\](.[^\[]*)\[\/EDIT\]", 
                "<table align=center style=\"width:100%\" cellpadding=5 cellspacing=1><TR><TD align=left style='border-right: #f6f6f6 1px solid; border-top:#f6f6f6 1px solid; border-left: #f6f6f6 1px solid; border-bottom: #f6f6f6 1px solid;background-color:#f6f6f6' width=\"100%\">$1</td></tr></table>", options);
            ubb = Regex.Replace(ubb, @"\[EDIT\]\[\/EDIT\]", "", options);
            ubb = Regex.Replace(ubb, @"<(.*?)(?:javascript|vbscript)\s*:(.*?)>", "<$1$2>", options);
            ubb = Regex.Replace(ubb, @"(<.*?style=.*?):expression(.*?>)", "$1$2", options);
            return ubb;
        }
        #endregion ubb编码转换End