public virtual void OnAuthorization(AuthorizationContext filterContext)
    {
        if (filterContext == null)
        {
            throw new ArgumentNullException("filterContext");
        }


        string auth = filterContext.HttpContext.Request.Headers["authorization"];

        if (!String.IsNullOrEmpty(auth))
        {
            byte[] encodedDataAsBytes = Convert.FromBase64String(auth.Replace("Basic ", ""));
            string val = Encoding.ASCII.GetString(encodedDataAsBytes);
            string userpass = val;
            string user = userpass.Substring(0, userpass.IndexOf(':'));
            string pass = userpass.Substring(userpass.IndexOf(':') + 1);

            if (!System.Web.Security.Membership.Provider.ValidateUser(user, pass))
            {
                filterContext.Result = new HttpUnauthorizedResult();
            }

        }
        else
        {
            if (AuthorizeCore(filterContext.HttpContext))
            {


                HttpCachePolicyBase cachePolicy = filterContext.HttpContext.Response.Cache;
                cachePolicy.SetProxyMaxAge(new TimeSpan(0));
                cachePolicy.AddValidationCallback(CacheValidateHandler, null /* data */);
            }
            else
            {
                // auth failed, redirect to login page
                filterContext.Result = new HttpUnauthorizedResult();
            }
        }


    }