CanvasAuthorize c# SDK无限循环

我正在寻找尝试并获得一个MVC3画布应用程序与Facebook c# SDK工作，但我正在努力允许权限-下面是我的代码，当我打开应用程序，我得到'允许/拒绝'对话框，但当我点击允许我得到重定向到我的应用程序和相同的对话框再次出现(并再次等等，无论我点击多少次允许)?

我想我错过了一些明显的东西…如果我把user_groups权限拿出来，它工作得很好，我只是不能访问人员组。

[CanvasAuthorize(Permissions = "user_groups")]
public class HomeController : Controller
{     
    public ActionResult Index()
    {
        IFacebookApplication settings = FacebookApplication.Current;
        if (settings != null)
        {
            //CanvasPage = settings.CanvasPage;
            //AppId = settings.AppId;
        }
        FacebookWebContext facebookContext = FacebookWebContext.Current;
        FacebookSignedRequest signedRequest = facebookContext.SignedRequest;
        var client = new FacebookWebClient(facebookContext.AccessToken);
        dynamic me = client.Get("me");
        var friends = client.Get("me/friends");
        var groups = client.Get("me/groups");
        ViewBag.Name = me.name;
        ViewBag.Id = me.id;
        JavaScriptSerializer sr = new JavaScriptSerializer();
        var fbFriends = sr.Deserialize<FBFriends>(friends.ToString());
        ViewData["friends"] = fbFriends.data;
        return View("Friends");
    }
}