using System;

public class Program

{

    public static void Main()

    {

        MyMain main = new MyMain();

        main.MyEvent += (sender, e) => Console.WriteLine("raised");

        main.RaiseInternally();

        main.Connect();

        main.external.RaiseExternally();

    }

}

​

public delegate void MyEventHandler(object Sender, EventArgs Args);

​

public class MyMain

{

     public event MyEventHandler MyEvent;

     public MyExternal external;

    public MyMain()

    {

    }

    public void RaiseInternally()

    {

        MyEvent?.Invoke(this, null); // <- wrong parameters, just an e.g.   

    }

    public void Connect()

    {

        external = new MyExternal(MyEvent);     

    }

}

​

public class MyExternal

{

     private MyEventHandler MyEvent;

     public MyExternal(MyEventHandler MyEvent)

     {

           this.MyEvent = MyEvent;

     }

    public void RaiseExternally()

    {

        MyEvent?.Invoke(this, null); // <- wrong parameters, just an e.g.

    }

}

​