using System;

​

namespace Test

{

    public class ThirdPartyLibrary

    {

        public delegate void dEeventRaiser();

        public event dEeventRaiser OnReceiveCall;

        public string IncomingCall(int x)

        {

​

            if (x > 0 && OnReceiveCall != null)

            { OnReceiveCall(); return "Valid "+x.ToString(); }

            return "Invalid"+x.ToString();

        }

    }

​

​

​

    public class EventSubscription

    {

​

        public EventSubscription()

        {

            ThirdPartyLibrary a = new ThirdPartyLibrary();

            a.OnReceiveCall += HandleTheCall;

            var iAnswer = a.IncomingCall(24198724);

            Console.WriteLine("Call received from "+iAnswer);

        }

​

        public virtual void HandleTheCall()

        {

            Console.WriteLine("Default way I handle the call");

        }

​

    }

​

    public class Program : EventSubscription

    {

        public override void HandleTheCall()

        {

            Console.WriteLine("Override sucessful, new way to handle the call ");

        }

​

     public static void Main(string [] args)

        {

​

          Program pb = new Program();  // Control goes EnventSubscription constructor as it is derived 

        }

​

    }

}