Strategy Design Pattern

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

The Strategy Design Pattern define as Encapsulates an algorithm inside a class by dofactory.com. This is the article I use to illustrate this Strategy Design Pattern.

The logical diagram of the Strategy Design Pattern as below.

image

We first create Strategy class. This class declares an interface common to all supported algorithms. Context uses this interface to call the algorithm defined by a ConcreteStrategy

interface class Strategy

{

 public abstract void AlgorithmInterface();

}

 

After this we create classes that consist of the supported algorithms. In this example there are 3 ConcreteStrategy implements the algorithm using the Strategy interface. The ConcreteStrategy could be implementing such as Quick Sort, Bubble Sort, and Selection Sort.

class ConcreteStrategyA : Strategy

{

    public override void AlgorithmInterface()

    {

        Console.WriteLine(

          “Called ConcreteStrategyA.AlgorithmInterface()”);

    }

}

 

class ConcreteStrategyB : Strategy

{

    public override void AlgorithmInterface()

    {

        Console.WriteLine(

          “Called ConcreteStrategyB.AlgorithmInterface()”);

    }

}

 

class ConcreteStrategyC : Strategy

{

    public override void AlgorithmInterface()

    {

        Console.WriteLine(

          “Called ConcreteStrategyC.AlgorithmInterface()”);

    }

}

 

Lastly, create a Context class. This create is configured with a ConcreteStrategy object. This create also maintains a reference to a Strategy object and may define an interface that lets Strategy access its data.

 

class Context

{

    private Strategy _strategy;

 

    // Constructor

    public Context(Strategy strategy)

    {

        this._strategy = strategy;

    }

 

    public void ContextInterface()

    {

        _strategy.AlgorithmInterface();

    }

}

 

The main program will look like below.

static void Main()

{

    Context context;

 

    // Three contexts following different strategies

    context = new Context(new ConcreteStrategyA());

    context.ContextInterface();

 

    context = new Context(new ConcreteStrategyB());

    context.ContextInterface();

 

    context = new Context(new ConcreteStrategyC());

    context.ContextInterface();

 

    // Wait for user

    Console.ReadKey();

}

   

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

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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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