public static string UbbDecode(string str)
{
str = HtmlEncode(str);
str = Regex.Replace(str, @"\(?<url>.+?)\", "<a href='${url}' target=_blank>${url}</a>", RegexOptions.Compiled RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"\(?<name>.+?)\", "<a href='${url}' target=_blank>${name}</a>", RegexOptions.Compiled RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"\(?<email>.+?)\", "<a href='mailt${email}' target=_blank>${email}</a>", RegexOptions.Compiled RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"\(?<name>.+?)\", "<a href='mailt${email}' target=_blank>${name}</a>", RegexOptions.Compiled RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"\(?<flash>.+?)\", "<div style='width:640;text-align:left'><a href='${flash}'>[\u5168\u5c4f\u67e5\u770b]</a></div><OBJECT codeBase=http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=4,0,2,0 classid=clsid:D27CDB6E-AE6D-11cf-96B8-444553540000 width=640 height=480><PARAM NAME=movie VALUE='${flash}'><PARAM NAME=quality VALUE=high><embed src='${flash}' quality=high pluginspage='http://www.macromedia.com/shockwave/download/index.cgi?P1_Prod_Version=ShockwaveFlash' type='application/x-shockwave-flash' width=640 height=480></embed></OBJECT>", RegexOptions.Compiled RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"\[dir=(?<width>[0-9]+?),(?<height>[0-9]+?)](?<url>.+?)\[/dir]", "<object classid=clsid:166B1BCA-3F9C-11CF-8075-444553540000 codebase=http://download.macromedia.com/pub/shockwave/cabs/director/sw.cab#version=7,0,2,0 width=${width} height=${height}><param name=src value=${url}><embed src=${url} pluginspage=http://www.macromedia.com/shockwave/download/ width=${width} height=${height}></embed></object>", RegexOptions.Compiled RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"\[rm=(?<width>[0-9]+?),(?<height>[0-9]+?)](?<url>.+?)\[/rm]", "<OBJECT classid=clsid:CFCDAA03-8BE4-11cf-B84B-0020AFBBCCFA class=OBJECT id=RAOCX width=${width} height=${height}><PARAM NAME=SRC VALUE=${url}><PARAM NAME=CONSOLE VALUE=Clip1><PARAM NAME=CONTROLS VALUE=imagewindow><PARAM NAME=AUTOSTART VALUE=true></OBJECT><br><OBJECT classid=CLSID:CFCDAA03-8BE4-11CF-B84B-0020AFBBCCFA height=32 id=video2 width=${width}><PARAM NAME=SRC VALUE=${url}><PARAM NAME=AUTOSTART VALUE=-1><PARAM NAME=CONTROLS VALUE=controlpanel><PARAM NAME=CONSOLE VALUE=Clip1></OBJECT>", RegexOptions.Compiled RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"\[mp=(?<width>[0-9]+?),(?<height>[0-9]+?)](?<url>.+?)\[/mp]", "<object align=middle classid=CLSID:22d6f312-b0f6-11d0-94ab-0080c74c7e95 class=OBJECT id=MediaPlayer width=${width} height=${height} ><param name=ShowStatusBar value=-1><param name=Filename value=${url}><embed type=application/x-oleobject codebase=http://activex.microsoft.com/activex/controls/mplayer/en/nsmp2inf.cab#Version=5,1,52,701 flename=mp src=${url} width=${width} height=${height}></embed></object>", RegexOptions.Compiled RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"\[qt=(?<width>[0-9]+?),(?<height>[0-9]+?)](?<url>.+?)\[/qt]", "<embed src=${url} width=${width} height=${height} autoplay=true loop=false controller=true playeveryframe=false cache=false scale=TOFIT bgcolor=#000000 kioskmode=false targetcache=false pluginspage=http://www.apple.com/quicktime/>", RegexOptions.Compiled RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"\[img](?<img>.+?)\[/img]", "<a href='${img}' target=_blank><img src='${img}' border=0 ></a>", RegexOptions.Compiled RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"\(?<text>.+?)\", "<font color='${color}'>${text}</font>", RegexOptions.Compiled RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"\(?<text>.+?)\", "<font face='${face}'>${text}</font>", RegexOptions.Compiled RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"\[down=(?<file>.+?)](?<text>.+?)\[/down]", "<a href='${file}' target='_blank'>${text}</a>", RegexOptions.Compiled RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"\[align=(?<align>.+?)](?<text>.+?)\[/align]", "<div align='${align}'>${text}</div>", RegexOptions.Compiled RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"\

(?<text>.+?)\

", "<div class=quote>${text}</div>", RegexOptions.Compiled RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"\(?<text>.+?)\", "<i>${text}</i>", RegexOptions.Compiled RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"\(?<text>.+?)\", "<u>${text}</u>", RegexOptions.Compiled RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"\(?<text>.+?)\", "<b>${text}</b>", RegexOptions.Compiled RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"\[size=(?<size>.+?)](?<text>.+?)\[/size]", "<font size='${size}'>${text}</font>", RegexOptions.Compiled RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"\[\*](?<text>.+?)\[/\*]", "<li>${text}</li>", RegexOptions.Compiled RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"\[list](?<text>.+?)\[/list]", "<ul>${text}</ul>", RegexOptions.Compiled RegexOptions.IgnoreCase);
return Regex.Replace(str, @"\[list=(?<type>.+?)](?<text>.+?)\[/list]", "<ol type=${type}>${text}</ol id=${type}>", RegexOptions.Compiled RegexOptions.IgnoreCase);
}
（出处：Viphot）