Access token error when trying to post a Facebook score in a canvas application

I'm trying to integrate the scoring system in my canvas app with Facebook's, implemented using MVC 3 and the 5.2.1.0 Facebook SDK.

A simplified hello-world variant of my game controller looks like:

public class MyController : Controller
{
  [CanvasAuthorize("publish_action" /*And some others*/)]
  public ActionResult Index()
  {
    var fb = new FacebookWebClient();
    var scores = fb.Get("/me/scores"); // Works (I think)
    fb.Post("/me/scores", new { score = 10 }); // Throws an exception
  }
}

The call to get scores looks like it's giving me something sensible; the call to write a score value throws "(OAuthException) (#15) This method must be called with an app access_token."

开发者_运维知识库What've I missed? The application id and secret are correctly set in my web.config - for example, I can successfully post an application apprequest in other parts of the actual application not shown in this stripped down test copy. Rummaging around with the debugger shows me that the FacebookWebClient object contains a non-empty access token field, and that that's included in the URI that fb.Post eventually uses.

The Facebook scores page (that Björn links to) mentions only publish_actions but I've tried including other pertinent sounding permissions, such as offline_access and user_games_activity to no effect.

I am assuming that the CanvasAuthorize attribute does the login correctly - it certainly seems to let me send an application apprequest, so it looks as if it's doing the right thing...

Your app needs the permission to write to the users profile. You can use the Graph API to request the required permissions from the user. If granted, Facebook will give you the required access token that you can then use in your request to Facebook. This practice ensures that you only perform actions, the user allowed you to.

Edit_: After looking at the docs: Are you sure you have the required permissions from the user like described here http://developers.facebook.com/docs/score/ ?

Please see this link. You'll need to get an facebook app. Using the apiId and SecretId, you can then post using the information in the link below. The key is adding &scope=manage_pages,offline_access,publish_stream to the url.

like so: "https://graph.facebook.com/oauth/access_token?client_id={0}&client_secret={1}&grant_type=client_credentials&scope=manage_pages,offline_access,publish_stream";