.NET策略(Strategy)模式

目录

定义 UML 参与者 示例

定义：

对算法的封装，是算法和责任分离。

UML:

代码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();
}
}
}[/code]

Output
QuickSorted list
Anna
Jimmy
Samual
Sandra
Vivek
ShellSorted list
Anna
Jimmy
Samual
Sandra
Vivek
MergeSorted list
Anna
Jimmy
Samual
Sandra
Vivek