Question

I’m trying to use the Facebook C# SDK to publish posts to the wall of a company page.
I need to do this from a batch job, so this is not a web app that any particular user is interacting with.
I have a Facebook application set up under my own Facebook ID, and I have granted it publish_stream, share_item, offline_access, and manage_pages permissions under my account. (I can verify that these permissions have been granted to the app under my Facebook settings page.) And the company page that I’m trying to post to is a page that I created myself, so I should have full access to it.

I am authenticating to Facebook with the app ID and secret for this application, getting an access token, putting together a message to post, then trying to post it. I get the following exception:

Facebook.FacebookOAuthException was unhandled by user code
Message=(OAuthException) (#200) The user hasn't authorized the application to perform this action

I’ve tried a few variations on the theme, but I can’t seem to figure out what I’m doing wrong.
Here’s a bit of my code:

        var client = new FacebookClient("APP ID", "SECRET");
        _log.DebugFormat("access token={0}", client.AccessToken);
        dynamic parameters = new ExpandoObject();
        parameters.message = "testing 123";
        /* fill in other parameters */
        dynamic result = client.Post(FanPageId+"/feed", parameters);
        /* here's where I get the exception */

I have seen references to pulling a page-specific access token out of the data returned from /me/accounts, but I can’t figure out how to do that from an offline app that’s authenticating as a Facebook app, rather than as a Facebook user.

UPDATE: I’ve gotten part of the way there by using this bit of code to connect to Facebook:

        var client = new FacebookClient("NON-EXPIRING OAUTH TOKEN");

…where the “non-expiring oauth token” is the one shown in the developer app on Facebook for the app in question.

This is still posting under my own ID though, so now I need to go the extra step of figuring out how to get the post to appear to come from the page itself.

Answer 1

I’ve figured this out now, so I’m going to answer my own question. This method allowed me to post to a fan page, under the ‘name’ of the fan page, without user intervention, using only Facebook.dll (not requiring Facebook.Web.dll).

// init with a non-expiring access token for an app that can manage the fan page
var client = new FacebookClient(fbAppOaToken);

// get accounts, using a Facebook ID for a user who has admin rights to the fan pge
dynamic accts = client.Get(string.Format("/{0}/accounts", fbAppAdminUser));

// find the access token for the fan page
string page_access_token = null;
foreach (var acct in accts.data)
{
    if (acct.id == fbFanPageId)
    {
        page_access_token = acct.access_token;
        break;
    }
}

// fill in parameters for the message to post
dynamic parameters = new ExpandoObject();
parameters.message = "testing 123";

// and include the access token as retrieved above
parameters.access_token = page_access_token;

dynamic result = client.Post(fbFanPageId + "/feed", parameters);

If anyone has a quicker or easier way of doing this, please let me know. I really just stumbled through this until I put enough puzzle pieces together to get this to work. Thanks.