UBB代碼轉HTML

string UbbToHtml(string input)    
 {   
            string ret;   
            ret = input.Replace("\r\n", "<br/>");  //換行 
            ret = ret.Replace(" ", "&nbsp");//空格
            //轉換顏色
            ret = System.Text.RegularExpressions.Regex.Replace(ret, @"\[COLOR=([^]]+)\]([^[]+)\[/COLOR\]", "<span style=\"color:$1;\">$2</span>", System.Text.RegularExpressions.RegexOptions.IgnoreCase);   
            //粗
            ret = System.Text.RegularExpressions.Regex.Replace(ret, @"\[B\]([^[]+)\[/B\]", "<b>$1</b>", System.Text.RegularExpressions.RegexOptions.IgnoreCase);   
            //斜
            ret = System.Text.RegularExpressions.Regex.Replace(ret, @"\[I\]([^[]+)\[/I\]", "<i>$1</i>", System.Text.RegularExpressions.RegexOptions.IgnoreCase);   
            //下劃線
            ret = System.Text.RegularExpressions.Regex.Replace(ret, @"\[U\]([^[]+)\[/U\]", "<u>$1</u>", System.Text.RegularExpressions.RegexOptions.IgnoreCase);   
            //居中
            ret = System.Text.RegularExpressions.Regex.Replace(ret, @"\[CENTER\]([^[]+)\[/CENTER\]", "<div align=\"center\">$1</div>", System.Text.RegularExpressions.RegexOptions.Ignore