public static string MapPath (string virtualPath)
    {
        if (virtualPath == null || virtualPath == "")
            throw new ArgumentNullException ("virtualPath");
        HttpContext context = HttpContext.Current;
        HttpRequest req = context == null ? null : context.Request;
        if (req == null) // ADDED for Orchard
            {
                var pp =  HostingEnvironment.ApplicationPhysicalPath;
                String vp=virtualPath;
                if (vp.IndexOf("~/") == 0)
		    {
			vp = pp + virtualPath.Substring(2);
                    }
                    // TODO: if not "~/" ???? then what?
                return vp;
            } // END added for Orchard
        else
            return req.MapPath (virtualPath);
    }