// Builds an absolute URL
    private static string BuildAbsolute(string relativeUri)
    {
        // get current uri
        Uri uri = HttpContext.Current.Request.Url;
        // build absolute path
        string app = HttpContext.Current.Request.ApplicationPath;
        if (!app.EndsWith("/")) app += "/";
        relativeUri = relativeUri.TrimStart('/');
        // return the absolute path
        return HttpUtility.UrlPathEncode(
          String.Format("http://{0}:{1}{2}{3}",
          uri.Host, uri.Port, app, relativeUri));
    }

    public static string ToProduct(string productId)
    {
        return BuildAbsolute(String.Format("Product.aspx?ProductID={0}", productId));
    }