using System;

public class Program

{   

    public delegate void Notify(int customerId, string message);

    public static void Main()

    {

        var notifs = new Notify(SendSMS);

        notifs += SendEmail;

        var orderProcessor = new OrderProcessor(notifs);

        orderProcessor.ProcessOrder(85620, 5384);

        orderProcessor.ProcessOrder(85621, 6378);

    }

    public static void SendSMS(int customerId, string message)

    {

        // Load the customer profile and get their mobile phone number

        // Send SMS to customer

        // Now that the email is successfully sent, we log to console:

        Console.WriteLine($"SMS sent to customer #{customerId} with message: {message}");

    }   

    public static void SendEmail(int customerId, string message)

    {

        // Load the customer profile and get their email address

        // Send email to customer

        // Now that the email is successfully sent, we log to console:

        Console.WriteLine($"Email sent to customer #{customerId} with message: {message}");

    }

    public class OrderProcessor

    {

        private readonly Notify _notifiers; // Just a reference to delegate, no collection

        public OrderProcessor(Notify notifiers)

        {

            _notifiers = notifiers;

        }

​

        public void ProcessOrder(int orderId, int customerId)

        {

            // Load the order from database

            // Process the order

            // The order is successfully processed!

            // Go ahead and send messages to customres

            _notifiers(customerId, $"Hi! Your order #{orderId} is on its way!");

        }   

    }

}

​