Get all followings using LINQ to Twitter

Question

I've just started a Windows Phone app, and I need to get all the user's followings. I tried this :

SharedState.Authorizer = pinAuth;
ITwitterAuthorizer auth = SharedState.Authorizer;
TwitterContext twitterCtx = new TwitterContext(auth);

var friendList =
    (from friend in twitterCtx.SocialGraph
        where friend.Type == SocialGraphType.Friends && friend.ScreenName == "_TDK"
        select friend)
    .SingleOrDefault();

List<String> Followings;
foreach (var id in friendList.ScreenName)
{
    Followings.Add(id.ToString());
}

But friendlist is always null and, obviously, the foreach does not like that and throws an exception.

Could someone help me ?

Thanks.

Answer 1

I think you need to iterate over the IDs collection, like this:

foreach (var id in friendList.IDs)
{
    Followings.Add(id.ToString());
}

You need to make async calls with Silverlight-based apps, including Windows Phone. Here's an example of how you can refactor the query:

var twitterCtx = new TwitterContext(auth);

(from social in twitterCtx.SocialGraph
 where social.Type == SocialGraphType.Followers &&
       social.ScreenName == "JoeMayo"
 select social)
.MaterializedAsyncCallback(asyncResponse =>
     Dispatcher.BeginInvoke(() =>
     {
         if (asyncResponse.Status != TwitterErrorStatus.Success)
         {
              MessageBox.Show(
                  "Error during query: " + 
                  asyncResponse.Exception.Message);
              return;
         }

         SocialGraph social = asyncResponse.State.SingleOrDefault();

         SocialListBox.ItemsSource = social.IDs;
     }));

The MaterializedAsyncCallback manages the callback from Twitter. Notice how I use Dispatcher.BeginInvoke to marshal the call back onto the UI thread as the callback is on a worker thread. On the asyncResponse callback parameter, use Status to see if there is an error and use State to get the data if the query is successful.