using System;

using System.Threading;

using System.Threading.Tasks;

public class Program

{

    public static void Main()

    {

        // Creating Instance of Publisher

            Publisher youtube = new Publisher("Youtube.Com", 2000);

            Publisher facebook = new Publisher("Facebook.com", 1000);

            //Create Instances of Subscribers

            Subscriber sub1 = new Subscriber("Florin");

            Subscriber sub2 = new Subscriber("Piagio");

            Subscriber sub3 = new Subscriber("Shawn");

            //Pass the publisher obj to their Subscribe function

            sub1.Subscribe(facebook);

            sub3.Subscribe(facebook);

            sub1.Subscribe(youtube);

            sub2.Subscribe(youtube);

            //sub1.Unsubscribe(facebook);

            //Concurrently running multiple publishers thread

            Task task1 = Task.Factory.StartNew(() => youtube.Publish());

            Task task2 = Task.Factory.StartNew(() => facebook.Publish());

            Task.WaitAll(task1, task2);

    }

}

public class NotificationEvent{

    public string NotificationMessage { get; private set; }

    public DateTime NotificationDate { get; private set; }

    public NotificationEvent(DateTime _dateTime, string _message)

    {

        NotificationDate = _dateTime;

        NotificationMessage = _message;

    }

}

public class Publisher{

    public string PublisherName { get; private set; }

    public int NotificationInterval { get; private set; }

    //** Declare an Event...

    // declare a delegate with any name

    public delegate void Notify(Publisher p, NotificationEvent e);

    // declare a variable of the delegate with event keyword

    public event Notify OnPublish;

    public Publisher(string _publisherName, int _notificationInterval){

        PublisherName = _publisherName;

        NotificationInterval = _notificationInterval;

    }

    //publish function publishes a Notification Event

    public void Publish(){

        while (true){

            Thread.Sleep(NotificationInterval); // fire event after certain interval

            if (OnPublish != null)

            {

                NotificationEvent notificationObj = new NotificationEvent(DateTime.Now, "New Notification Arrived from");

                OnPublish(this, notificationObj);

            }

            Thread.Yield();

        }

    }

}

public class Subscriber{

​

    public string SubscriberName { get; private set; }

​

    public Subscriber(string _subscriberName){

        SubscriberName = _subscriberName;

    }

    // This function subscribe to the events of the publisher

    public void Subscribe(Publisher p){

​

        // register OnNotificationReceived with publisher event

        p.OnPublish += OnNotificationReceived;  // multicast delegate 

​

    }

​

    // This function unsubscribe from the events of the publisher

    public void Unsubscribe(Publisher p){

​

        // unregister OnNotificationReceived from publisher

        p.OnPublish -= OnNotificationReceived;  // multicast delegate 

    }

​

    // It get executed when the event published by the Publisher

    protected virtual void OnNotificationReceived(Publisher p, NotificationEvent e){

        Console.WriteLine("Hey " + SubscriberName + ", " + e.NotificationMessage +" - "+ p.PublisherName + " at " + e.NotificationDate);

    }

}