Querying for Epic Friends and their status

When you run the app and trigger Auth login, you should now see the updated consent screen in the browser and still be able to successfully complete authentication.

Querying for friends

Now that that’s added, let’s start implementing the query functionality in our solution:
 

1. Add a new UserControl to the Views folder, called FriendsView
2. Paste in the following XAML, replacing the empty Grid node:

• We’ll use a ListView to display the friends we get back from the API and have additional buttons to subscribe and unsubscribe to/from updates, as well as query for friend’s presence.

 

3. Open FriendsView.xaml.cs and define the DataContext:

• Note the empty FriendsListView_SelectionChanged event handler, which we’ll use later when we implement friend presence status querying.

 

4. As we’ll combine a few things in our UI to display friends (Epic Account Id, Friend status, Presence status), create a new folder called Models to the root of the project and add a Friend.cs class:

5. Add a FriendsViewModel.cs class to the ViewModels folder:

6. Add a static reference to FriendsViewModel to ViewModelLocator:

7. Add a FriendsService.cs class to the Services folder:

• We instantiate an options class, pass it to the QueryFriends API on the Friends Interface, retrieve the count from cache, and iterate to retrieve the status for each friend.
• We then add the friend, including friend status, to the ViewModel to be displayed in the UI.

 

8. Add a FriendsQueryCommand.cs class to the Commands folder:

9. Now open FriendsViewModel.cs again and instantiate FriendsQueryCommand:

10. Add the following line in the ViewModelLocator RaiseAuthCanExecuteChanged() method to ensure that the Query presence button is only enabled when a user is logged in:

11. Finally, add the PresenceView to our MainWindow TabControl:

Now we can run the app, authenticate, and consent to the updated permissions in the browser, after which we’ll be able to use the Query friends button to get the player’s friends and status. As expected, however, we won’t get any friends back from the API, as none of them have consented to our application. Let’s fix that.

Getting consent from a friend

To validate our code, we have to get a friend to consent to our application. Note that only friends who have accepted your friend request will be returned by the QueryFriends API we implemented. If this were an actual game we were developing, we could complete a Brand Review submission for our application and share our game with a friend to get consent. 

However, as we’re only developing this sample, we’ll have to add a friend to our Developer Portal Organization, as otherwise they will not be able to access our application. This is done to protect Epic Games ecosystem users, you (the developer), other game developers, and Epic Games from brand spoofing, phishing, and more.
 

1. Log in to the Developer Portal at https://dev.epicgames.com/portal/.
2. Click on the Organization tab on the left and use the blue Invite button to invite a friend, selecting an appropriate Role.

 
Now our friend has to run our sample application, connecting to our product, client, sandbox, and deployment. Package and share the following files from the /bin/ directory of the project:
 

• EOSCSharpSample.dll
• EOSCSharpSample.exe
• EOSCSharpSample.runtimeconfig.json
• EOSSDK-Win32-Shipping.dll

The first time they run the application, they will get prompted for consent, and should see our account show up when Querying friends. Subsequently, when we do the same after the friend has provided consent, their account will show up when Querying friends.
 
Note that we only see friends’ Epic Account ID and not their display name, but you can use the same QueryUserInfo call we used in AuthService.Login() to retrieve more information for each friend. The status column will always display “Offline” at this point, as that’s the 0 value of the Epic.OnlineServices.Presence.Status enum, but we’ll tackle that further in this article.

Subscribing to updates

Once you’ve queried for friends, you should subscribe to notifications when the friend status changes (rather than query again). The Friends Interface will return one of these four statuses for a friend, per the Epic.OnlineServices.Friends.FriendsStatus enum: NotFriends, InviteSent, InviteReceived, Friends. While there are no APIs to manage friends directly, as mentioned earlier, we still need to subscribe to updates so we know when a friend request is accepted or someone is unfriended. The Friends Interface provides APIs to subscribe and unsubscribe to these updates, so let’s implement them.
 

1. Open FriendsService.cs and add the following methods:

• We call AddNotifyFriendsUpdate, passing in empty options, to get a Notification ID back, which both confirms that the notification has been set up and we’ll need to use to unsubscribe from updates (as seen in UnsubscribeUpdates()).
• We then define a callback method with the functionality we want when a notification is sent. In this case we simply add another record to the Friends list with the new status.

 

2. We’ll also add a trigger to these commands’ CanExecuteChanged behaviors, so they’re only available after we do an initial query for friends:

Add:

Below the following lines in FriendsService.QueryFriends():

[...]
var friendStatus = App.Settings.PlatformInterface.GetFriendsInterface().GetStatus(getStatusOptions);

        ViewModelLocator.Friends.Friends.Add(new Friend()
        {
            EpicAccountId = friend,
            FriendsStatus = friendStatus
        });
    }
}
 

3. Add a FriendsSubscribeUpdatesCommand.cs class to the Commands folder:

4. Add a FriendsUnsubscribeUpdatesCommand.cs class to the Commands folder:

5. Declare and initialize our new command in FriendsViewModel.cs:

Now when we run the app, we can query for friends and subscribe/unsubscribe updates. Once subscribed for updates, you can remove a listed friend through the Epic Games Launcher and you’ll see a new entry appear for that friend in the ListView with a status of NotFriends.

Querying for friends presence

The last thing for us to do is implement the functionality to query for friends’ presence status, building on what we implemented in the last article. Now we can make use of QueryPresence to retrieve presence for each friend. 
 

1. Open PresenceQueryCommand from the Commands folder and replace both methods with the following code:

• We modify the CanExecute code to also check for a parameter (the selected Friend we’ll pass from our FriendsView ListView) and add the “else” statement to Execute to call PresenceService.Query() when a Friend is passed.

 

2. Open FriendsViewModel and instantiate PresenceQueryCommand:

3. Finally, add the following to the FriendsListView_SelectionChanged event handler in FriendsView.xaml.cs to ensure the query status button is only enabled when a friend is selected:

Now when we run the application, hit Query friends, select a friend that’s online, and hit Query status, we’ll see their status update in the UI.
 
As mentioned in the previous article, you should implement AddNotifyOnPresenceChanged in a production game to get notified when there’s a change in presence status for friends.

Get the code

Get the code for this article below (follow step five and ten of this article to add the SDK to the solution, and add your SDK credentials to ApplicationSettings.cs).