deviceToken of IOS Device

In your FinishedLaunching method, register the app for remote notifications, through the UIApplication object you get in it:

// Pass the UIRemoteNotificationType combinations you want
app.RegisterForRemoteNotificationTypes(UIRemoteNotificationType.Alert |
 UIRemoteNotificationType.Sound);

Then, in your AppDelegate class, override the RegisteredForRemoteNotifications method:

public override void RegisteredForRemoteNotifications (UIApplication application, NSData deviceToken)
{
    // The device token
    byte[] token = deviceToken.ToArray();
}

You also have to override the FailedToRegisterForRemoteNotifications method, to handle the error, if any:

public override void FailedToRegisterForRemoteNotifications (UIApplication application, NSError error)
{
    // Do something with the error
}