using System;

using System.Threading.Tasks;

public class Program

{

    public static void Main()

    {

        Add obj = new Add();

        obj.WhereToSend = DisplayAdd;

        Console.WriteLine("Started Calculating");

        obj.Calculate(10).Wait();

    }

    static async Task DisplayAdd(int value)

    {

        Console.WriteLine("In Display Add");

        // Some awaitable operation like below

        await Task.Delay(1);

        Console.WriteLine("value :" + value);

    }

}

​

    public delegate Task SendResult(int i);

    public class Add

    {   

        public SendResult WhereToSend;

​

        public async Task Calculate (int number)

        {

            Console.WriteLine("Entered");

            int result = number + number;

            await WhereToSend (result);

            Console.WriteLine("Finished");

        }

    }