Посредник (Mediator)

using System;
using System.Collections.Generic;
using System.Text;
using System.Threading;
using System.Linq;
using System.Threading.Tasks;

class Program
{
   static void Main(string[] args)
   {
    ManagerMediator mediator = new ManagerMediator();
    Collegue customer = new CustomerCollegue(mediator);
    Collegue programmer = new ProgrammerCollegue(mediator);
    Collegue tester = new TesterCollegue(mediator);
    mediator.Customer = customer;
    mediator.Programmer = programmer;
    mediator.Tester = tester;
    customer.Send("Есть заказ, надо сделать программу");
    programmer.Send("Программа сделана, надо провести тест");
    tester.Send("Программа протестирована и готова к продаже");

    Console.ReadLine();
   }
}

abstract class Mediator
{
    public abstract void Send(string msg, Collegue collegue);
}

abstract class Collegue
{
    protected Mediator mediator;

    public Collegue(Mediator mediator)
    {
        this.mediator = mediator;
    }

    public virtual void Send(string message)
    {
        mediator.Send(message, this);
    }

    public virtual void Notify(string message)
    {
        Console.WriteLine("Сообщение заказчику: " + message);
    }
}

class CustomerCollegue : Collegue
{
    public CustomerCollegue(Mediator mediator) : base(mediator)
    {

    }

    public override void Notify(string message)
    {
        Console.WriteLine("Сообщение заказчику " + message);
    }
}

class ProgrammerCollegue : Collegue
{
    public ProgrammerCollegue(Mediator mediator) : base(mediator)
    {

    }

    public override void Notify(string message)
    {
        Console.WriteLine("Сообщение программисту " + message);
    }
}

class TesterCollegue : Collegue
{
    public TesterCollegue(Mediator mediator) : base(mediator)
    {

    }

    public override void Notify(string message)
    {
        Console.WriteLine("Сообщение тестеру " + message);
    }
}

class ManagerMediator : Mediator
{
    public Collegue Customer{get;set;}
    public Collegue Programmer{get;set;}
    public Collegue Tester{get;set;}

    public override void Send(string msg, Collegue collegue)
    {
        if(Customer == collegue)
            Programmer.Notify(msg);
        else if(Programmer == collegue)
            Tester.Notify(msg);
        else if(Tester == collegue)
            Customer.Notify(msg);
    }
}