Xamarin iOS SDK

public override void RegisteredForRemoteNotifications(UIApplication application, NSData deviceToken)
{
    PushNotificationManager.PushManager.HandlePushRegistration (deviceToken);
}

public override void FailedToRegisterForRemoteNotifications(UIApplication application, NSError error)
{
    PushNotificationManager.PushManager.HandlePushRegistrationFailure (error);
}

public override void ReceivedRemoteNotification(UIApplication application, NSDictionary userInfo)
{
     PushNotificationManager.PushManager.HandlePushReceived (userInfo);
}

PushNotificationManager pushmanager = PushNotificationManager.PushManager;
pushmanager.Delegate = new PushDelegate();
UNUserNotificationCenter.Current.Delegate = pushmanager.notificationCenterDelegate;

if (options != null) {
     if (options.ContainsKey (UIApplication.LaunchOptionsRemoteNotificationKey)) {
       pushmanager.HandlePushReceived(options);
     }
}

pushmanager.RegisterForPushNotifications();

public class PushDelegate : PushNotificationDelegate
       {
           public override void OnPushAccepted(PushNotificationManager pushManager, NSDictionary pushNotification)
           {
               Console.WriteLine(“Push accepted: ” + pushNotification);
           }

           public override void OnPushReceived(PushNotificationManager pushManager, NSDictionary pushNotification, bool onStart)
           {
               Console.WriteLine(“Push received: ” + pushNotification);
           }

           public override void OnDidRegisterForRemoteNotificationsWithDeviceToken(NSString token)
           {
               Console.WriteLine(“Registered for push notifications: ” + token);
           }

           public override void OnDidFailToRegisterForRemoteNotificationsWithError(NSError error)
           {
               Console.WriteLine(“Error: ” + error);
           }
       }