Observer Design Pattern

Infosys.cs

using System;
using System.Collections.Generic;

namespace ObserverPattern
{
    //concrete subject
    public class Infosys : Subject
    {
        public Infosys(string name, double price) : base(name, price) { }
    }
}

IStockPriceWatcher.cs

using System;
using System.Collections.Generic;

namespace ObserverPattern
{
    //Observer
    public interface IStockPriceWatcher
    {
        string Name { get; set; }
        Subject Subject { get; set; }
        void Update(Subject sub);
    }
}

Program.cs

using System;
using System.Collections.Generic;

namespace ObserverPattern
{
    class Program
    {
        static void Main(string[] args)
        {
            //subjects
            TCS tcs = new TCS("TCS", 3000);
            Infosys infy = new Infosys("Infosys", 1100);
            Wipro wipro = new Wipro("Wipro", 350);

            //watchers
            Watcher watcher1 = new Watcher("Watcher1");
            Watcher watcher2 = new Watcher("Watcher2");
            Watcher watcher3 = new Watcher("Watcher3");

            Console.WriteLine(new string('-',30));
            tcs.Subscribe(watcher1);
            infy.Subscribe(watcher2);
            wipro.Subscribe(watcher3);

            Console.WriteLine(new string('-', 30));
            tcs.Price = 3100;
            infy.Price = 1050;
            wipro.Price = 355;

            Console.WriteLine(new string('-', 30));
            tcs.UnSubscribe(watcher1);
            infy.UnSubscribe(watcher2);

            Console.WriteLine(new string('-', 30));
            tcs.Price = 3170;
            infy.Price = 1060;

            Console.WriteLine(new string('-', 30));
            tcs.Subscribe(watcher2);
            infy.Subscribe(watcher1);

            Console.WriteLine(new string('-', 30));
            tcs.Price = 3200;
            infy.Price = 1070;

            Console.Read();
        }
    }
}

Subject.cs

using System;
using System.Collections.Generic;

namespace ObserverPattern
{
    //subject
    public abstract class Subject
    {
        private string name;
        private double price;
        private List<IStockPriceWatcher> investors = new List<IStockPriceWatcher>();
        public Subject(string Name, double Price)
        {
            name = Name;
            price = Price;
        }
        public string Name
        {
            get { return name; }
        }
        public double Price
        {
            get { return price; }
            set
            {
                if (price != value)
                {
                    price = value;
                    Notify();
                }
            }
        }
        public void Subscribe(IStockPriceWatcher observer)
        {
            investors.Add(observer);
            observer.Subject = this;
            Console.WriteLine("{0} subscribed to {1}", observer.Name, name);
        }
        public void UnSubscribe(IStockPriceWatcher observer)
        {
            investors.Remove(observer);
            Console.WriteLine("{0} unsubscribed from {1}", observer.Name, name );
        }
        public void Notify()
        {
            investors.ForEach(x => x.Update(this));
        }
    }
}

TCS.cs

using System;
using System.Collections.Generic;

namespace ObserverPattern
{
    //concrete subject
    public class TCS : Subject
    {
        public TCS(string name, double price) :base (name, price) { }
    }
}

Watcher.cs

using System;
using System.Collections.Generic;

namespace ObserverPattern
{
    //concrete observer
    public class Watcher : IStockPriceWatcher
    {
        public string Name { get; set; }
        public Subject Subject { get ; set ; }
        public Watcher(string name)
        {
            Name = name;
        }
        public void Update(Subject sub)
        {
            Console.WriteLine("{0}, {1} price udated to {2}",Name, Subject.Name, Subject.Price);
        }
    }
}

Wipro.cs

using System;
using System.Collections.Generic;

namespace ObserverPattern
{
    //concrete subject
    public class Wipro : Subject
    {
        public Wipro(string name, double price) : base(name, price) { }
    }
}