Strategy Pattern

strategy.cs

using System;

using System.Collections.Generic;

 

namespace DoFactory.GangOfFour.Strategy.RealWorld

{

  /// <summary>

  /// MainApp startup class for Real-World 

  /// Strategy Design Pattern.

  /// </summary>

  class MainApp

  {

    /// <summary>

    /// Entry point into console application.

    /// </summary>

    static void Main()

    {

      // Two contexts following different strategies

      SortedList studentRecords = new SortedList();

 

      studentRecords.Add("Samual");

      studentRecords.Add("Jimmy");

      studentRecords.Add("Sandra");

      studentRecords.Add("Vivek");

      studentRecords.Add("Anna");

 

      studentRecords.SetSortStrategy(new QuickSort());

      studentRecords.Sort();

 

      studentRecords.SetSortStrategy(new ShellSort());

      studentRecords.Sort();

 

      studentRecords.SetSortStrategy(new MergeSort());

      studentRecords.Sort();

 

      // Wait for user

      Console.ReadKey();

    }

  }

 

  /// <summary>

  /// The 'Strategy' abstract class

  /// </summary>

  abstract class SortStrategy

  {

    public abstract void Sort(List<string> list);

  }

 

  /// <summary>

  /// A 'ConcreteStrategy' class

  /// </summary>

  class QuickSort : SortStrategy

  {

    public override void Sort(List<string> list)

    {

      list.Sort(); // Default is Quicksort

      Console.WriteLine("QuickSorted list ");

    }

  }

 

  /// <summary>

  /// A 'ConcreteStrategy' class

  /// </summary>

  class ShellSort : SortStrategy

  {

    public override void Sort(List<string> list)

    {

      //list.ShellSort(); not-implemented

      Console.WriteLine("ShellSorted list ");

    }

  }

 

  /// <summary>

  /// A 'ConcreteStrategy' class

  /// </summary>

  class MergeSort : SortStrategy

  {

    public override void Sort(List<string> list)

    {

      //list.MergeSort(); not-implemented

      Console.WriteLine("MergeSorted list ");

    }

  }

 

  /// <summary>

  /// The 'Context' class

  /// </summary>

  class SortedList

  {

    private List<string> _list = new List<string>();

    private SortStrategy _sortstrategy;

 

    public void SetSortStrategy(SortStrategy sortstrategy)

    {

      this._sortstrategy = sortstrategy;

    }

 

    public void Add(string name)

    {

      _list.Add(name);

    }

 

    public void Sort()

    {

      _sortstrategy.Sort(_list);

 

      // Iterate over list and display results

      foreach (string name in _list)

      {

        Console.WriteLine(" " + name);

      }

      Console.WriteLine();

    }

  }

}