Catching MainActivity Events in App.xaml.cs

I have this in my App.xaml.cs

CrossFirebasePushNotification.Current.OnNotificationReceived += (s, p) =>
{                    
   System.Diagnostics.Debug.WriteLine("Received");
};

When I receive messages, that is, have something on pdata, how do I fire on my badge's MainActivity?

In the OnCreate of Activity I have

badge = new Badge();

And I need to create a method or something else to fire the badge counter, like this:

Contador++;
badge.count(Contador);

I can not get anything in the App from the MainActivity or the other way around, even adding the appropriate references.

That lambda is inside the App.xaml.cs class constructor.