currDir = Server.MapPath(".");
 parentDir = Server.MapPath("..");
 rootDir = Server.MapPath("/");

Will man Server.MapPath in Klassen verwenden > dann:

  HttpContext.Current.Server.MapPath();

Quellen:
http://www.devx.com/vb2themax/Tip/18488
http://glengamoi.com/forums/p/3066/10836.aspx
http://msdn.microsoft.com/de-de/library/system.web.httpserverutility.mappath(VS.80).aspx