Console app utilizing Facebook offline_access extended permissions and Facebook C# SDK

Question

I'm a refugee from the old Facebook Developer Toolkit porting my app to the newer Facebook C# SDK. I've got the MVC web app side of my solution worked out, but I also have a console application that I run in batch as part of my overall solution. I obtain the offline_access extended permission for all of my users and store the non-expiring session key for later use in my console app.

With the Facebook Developer Toolkit I was able to spin up a Connect Session and REST api using my API Key, API Secret, and the saved user session key and make Facebook api calls.

In the Facebook C# SDK the non-web samples seem to rely on popping up some kind of browser control for interactive user login. That won't work for a console batch application processing users offline.

I've got this far:

string oAuthAccessToken = "{access token}"
var app = new Facebook.FacebookApp(oAuthAccessToken );

// now I can make api calls like this:
dynamic currentPermissionsJson = new ExpandoObject();
currentPermissionsJson = app.Query(string.Format("SELECT publish_stream, offline_access, email from permissions where uid = {0}", {userid}));
var currentPermissions = ((JsonArray)currentPermissionsJson)[0] as IDictionary<string, object>;

and away we go.

I'm just stuck on how to convert my existing stored session keys to Facebook OAuth access tokens. I can see how I can construct POSTs to https://graph.facebook.com/oauth/exchange_sessions with params such as

client_id={my app id}
&client_secret={my app secret}
&sessions={previously stored session keys}

and get the access token back in the response.

But I'm thinking the SDK must offer some method of doing this for me. Or does it?

Answer 1

Unfortunately, we dont have any helpers in the current Facebook C# SDK to exchange the access tokens. I have created an issue and I will try to get it in there shortly. http://facebooksdk.codeplex.com/workitem/5788

For now I wrote up this. Give it a try and let me know how it works:

public class FacebookOAuth
{

    public static IEnumerable<ExchangeSessionResult> ExchangeSessions(string appId, string appSecret, params string[] sessionKeys)
    {
        WebClient client = new WebClient();
        var dict = new Dictionary<string, object>();
        dict.Add("client_id", appId);
        dict.Add("client_secret", appSecret);
        dict.Add("sessions", String.Join(",", sessionKeys));
        string data = dict.ToJsonQueryString();
        string result = client.UploadString("https://graph.facebook.com/oauth/exchange_sessions", data);
        return Newtonsoft.Json.JsonConvert.DeserializeObject<ExchangeSessionResult[]>(result);
    }

}

public class ExchangeSessionResult
{

    [Newtonsoft.Json.JsonProperty("access_token")]
    public string AccessToken { get; set; }

    [Newtonsoft.Json.JsonProperty("expires")]
    public string Expires { get; set; }

}