Mediator design pattern

This short article shows you have to build Observer design pattern in C#.

The simplest example is still from dofactory.com http://www.dofactory.com/net/mediator-design-pattern.

Mediator design pattern defines simplified communication between classes.

Logical diagram of Mediator design pattern below.

clip_image001

 

Firstly, we create Mediator class defines an interface for communicating with Colleague objects.

abstract class Mediator

{

    public abstract void Send(string message,

      Colleague colleague);

}

 

Second class to create is ConcreteMediator class. It is to implements cooperative behavior by coordinating Colleague objects and knows and maintains its colleagues

class ConcreteMediator : Mediator

{

    private ConcreteColleague1 _colleague1;

    private ConcreteColleague2 _colleague2;

 

    public ConcreteColleague1 Colleague1

    {

        set { _colleague1 = value; }

    }

 

    public ConcreteColleague2 Colleague2

    {

        set { _colleague2 = value; }

    }

 

    public override void Send(string message,

      Colleague colleague)

    {

        if (colleague == _colleague1)

        {

            _colleague2.Notify(message);

        }

        else

        {

            _colleague1.Notify(message);

        }

    }

}

 

Finally we create a Colleague and two ConcreteColleague classes. This class knows its Mediator object and each colleague communicates with its mediator whenever it would have otherwise communicated with another colleague.

abstract class Colleague

{

    protected Mediator mediator;

 

    // Constructor

    public Colleague(Mediator mediator)

    {

        this.mediator = mediator;

    }

}

 

class ConcreteColleague1 : Colleague

{

    // Constructor

    public ConcreteColleague1(Mediator mediator)

        : base(mediator)

    {

    }

 

    public void Send(string message)

    {

        mediator.Send(message, this);

    }

 

    public void Notify(string message)

    {

        Console.WriteLine(“Colleague1 gets message: “

          + message);

    }

}

 

class ConcreteColleague2 : Colleague

{

    // Constructor

    public ConcreteColleague2(Mediator mediator)

        : base(mediator)

    {

    }

 

    public void Send(string message)

    {

        mediator.Send(message, this);

    }

 

    public void Notify(string message)

    {

        Console.WriteLine(“Colleague2 gets message: “

          + message);

    }

}

The main program will look like below.

static void Main()

{

    ConcreteMediator m = new ConcreteMediator();

 

    ConcreteColleague1 c1 = new ConcreteColleague1(m);

    ConcreteColleague2 c2 = new ConcreteColleague2(m);

 

    m.Colleague1 = c1;

    m.Colleague2 = c2;

 

    c1.Send(“How are you?”);

    c2.Send(“Fine, thanks”);

 

    // Wait for user

    Console.ReadKey();

}

 

You can also download a single solution from http://skydrive.live.com. The sample file name is ConAppMediator.zip. My MSN ID is chanmmn@hotmail.com.

About chanmingman

Since March 2011 Microsoft Live Spaces migrated to Wordpress (http://www.pcworld.com/article/206455/Microsoft_Live_Spaces_Moves_to_WordPress_An_FAQ.html) till now, I have is over 1 million viewers. This blog is about more than 50% telling you how to resolve error messages, especial for Microsoft products. The blog also has a lot of guidance teaching you how to get stated certain Microsoft technologies. The blog also uses as a help to keep my memory. The blog is never meant to give people consulting services or silver bullet solutions. It is a contribution to the community. Thanks for your support over the years. Ming Man is Microsoft MVP since year 2006. He is a software development manager for a multinational company. With 25 years of experience in the IT field, he has developed system using Clipper, COBOL, VB5, VB6, VB.NET, Java and C #. He has been using Visual Studio (.NET) since the Beta back in year 2000. He and the team have developed many projects using .NET platform such as SCM, and HR based applications. He is familiar with the N-Tier design of business application and is also an expert with database experience in MS SQL, Oracle and AS 400.
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