EventsSample

namespace UnitTestingClasses
{
    using System;
    using System.Collections.Generic;
    using System.Linq;

    public class Startup
    {
        public static void Main()
        {
            Inbox personsInbox = new Inbox();
            Person person = new Person("Ivan", personsInbox);

            Website website = new Website(@"https://www.softuni.bg");
            website.SubscribeToNews(person);

            News firstNews = new News("first");
            website.PostNews(firstNews);
            News secondNews = new News("second");
            website.PostNews(secondNews);

            List<News> notificationNews = person.GetNewsFromNotifications();
            string titles = string.Join(Environment.NewLine, notificationNews.Select(n => n.Title));
            Console.WriteLine(titles);
        }
    }

    public class Inbox
    {
        private List<News> news;

        public Inbox()
        {
            this.news = new List<News>();
        }

        public List<News> News
        {
            get
            {
                return this.news.ToList();
            }
        }

        public void AddNewsNotification(News news)
        {
            this.news.Add(news);
        }
    }

    public class Person
    {
        private string name;
        private Inbox inbox;

        public Person(string name, Inbox inbox)
        {
            this.name = name;
            this.inbox = inbox;
        }

        public void NewsPostedEventHandler(object sender, WebsiteEventArgs websiteEventArgs)
        {
            News news = websiteEventArgs.News;
            this.inbox.AddNewsNotification(news);
        }

        public List<News> GetNewsFromNotifications()
        {
            return this.inbox.News;
        }
    }

    public delegate void NewsPostedEventHandler(object sender, WebsiteEventArgs websiteEventArgs);

    public class Website
    {
        private event NewsPostedEventHandler NewsPosted;

        public Website(string url)
        {
            this.Url = url;
        }

        public string Url { get; set; }

        protected virtual void OnNewsPosted(WebsiteEventArgs websiteEventArgs)
        {
            this.NewsPosted?.Invoke(this, websiteEventArgs);
        }

        public void PostNews(News news)
        {
            WebsiteEventArgs websiteEventArgs = new WebsiteEventArgs(news);
            this.OnNewsPosted(websiteEventArgs);
        }

        public void SubscribeToNews(Person person)
        {
            this.NewsPosted += person.NewsPostedEventHandler;
        }
    }

    public class WebsiteEventArgs : EventArgs
    {
        public WebsiteEventArgs(News news)
        {
            this.News = news;
        }

        public News News { get; set; }
    }

    public class News
    {
        private string title;

        public News(string title)
        {
            this.Title = title;
        }

        public string Title
        {
            get
            {
                return this.title;
            }

            private set
            {
                this.title = value;
            }
        }
    }
}