using System;

​

public class Program

{

    public static void Main(string[] args)

    {

        Action<int> handleIterationComplete = (int s) => Console.WriteLine($"Iteration {s} complete.");

        var p = new ProgramClass();

        p.Callee(handleIterationComplete);

    }

}

​

public class ProgramClass

{

    public void Callee(Action<int> iterationCompleteHandler)

    {

        for (int i=0; i<10; i++)

        {

            //do some work

            Console.WriteLine($"Doing Iteration {i}");

​

            //post a notification

            iterationCompleteHandler(i);

        }

    }

}