策略模式（Strategy）:它定义了算法家族，分别封装起来，让它们之间可以互相替换，此模式让算法的变化，不会影响到使用算法的客户。

--《HeadFirst设计模式》

一般来说这些算法完成的工作都是一样的，只是它们的实现不一样而已，通过策略模式可以定义一个公共的接口去调用不同的算法类，从而降低了算法类和调用算法类的耦合度。

关键字：策略模式，接口，抽象类，继承

1        策略模式分析

class StrategyA : Strategy
{
public override void AlgorithmInterface()
{
Console.WriteLine("算法A实现");
}
}

class StrategyB : Strategy
{
public override void AlgorithmInterface()
{
Console.WriteLine("算法B实现");
}
}

class StrategyC : Strategy
{
public override void AlgorithmInterface()
{
Console.WriteLine("算法C实现");
}
}

class Context
{
private Strategy strategy = null;

public Context(string type)
{
switch(type)
{
case "A":
this.strategy = new StrategyA(); //instance the object
break;
case "B":
this.strategy = new StrategyB();
break;
case "C":
this.strategy = new StrategyC();
break;
}
}

public void ContextInterface()
{
strategy.AlgorithmInterface();
}

}

class Context
{
private Strategy strategy = null;
private static readonly string path = ConfigurationManager.AppSettings["Strategy"];
string className = string.Empty;

public Context(string type)
{

switch(type)
{
case "A":
//this.strategy = new StrategyA(); //instance the object
className = path + ".StrategyA";
this.strategy = (StrategyModel.StrategyA)Assembly.Load(path).CreateInstance(className);
break;
case "B":
//this.strategy = new StrategyB();
className = path + ".StrategyB";
this.strategy = (StrategyModel.StrategyB)Assembly.Load(path).CreateInstance(className);
break;
case "C":
//this.strategy = new StrategyC();
className = path + ".StrategyC";
this.strategy = (StrategyModel.StrategyC)Assembly.Load(path).CreateInstance(className);
break;
}
}

public void ContextInterface()
{
strategy.AlgorithmInterface();
}

}