using System;

using System.Collections.Immutable;

​

namespace ThisWorld

{

    public static class MessageSenderExtensions

    {

        public static void SendMessage(this MessageSenderBase sender, string content)

        {

            string headerNoti = sender switch

            {

                EmailSender eSender => "Email sent: ", 

                SmsSender sSender => "SMS message sent: ", 

                FacebookSender fbSender => "Facebook message sent: ", 

                _ => throw new ArgumentException($"Something wicked happened: {nameof(sender)}")

            };

            Console.WriteLine($"{headerNoti}{content}");

        }

    }

    public abstract class MessageSenderBase

    {

        public static void SendMessage(string content) {}

    }

​

    public class EmailSender : MessageSenderBase

    {

        // public void SendMessage(string content) => Console.WriteLine($"Email sent: {content}");

    }

​

    public class SmsSender : MessageSenderBase

    {

        // public void SendMessage(string content) => Console.WriteLine($"SMS message sent: {content}");

    }

​

    public class FacebookSender : MessageSenderBase

    {

        // public void SendMessage(string content) => Console.WriteLine($"Facebook message sent: {content}");

    }

​

    public class Program

    {

        public static void Main()

        {

            var eSender = new EmailSender();

            var fbSender = new FacebookSender();

            var smsSender = new SmsSender();

            var senders = ImmutableList<MessageSenderBase>.Empty;

            senders = senders.Add(eSender);

            senders = senders.Add(fbSender);

            senders = senders.Add(smsSender);

            foreach (var sender in senders) {

                sender.SendMessage("hello God");

            }

        }

    }

}