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

策略模式结构图：

策略模式实现代码：

abstract class Strategy{	public abstract void AlgorithmInterface();	}class ConcreStrategyA:Strategy{	public override void AlgorithmInterface();	{		console.WriteLine("算法A实现");	}}class ConcreStrategyB:Strategy{	public override void AlgorithmInterface();	{		console.WriteLine("算法B实现");	}}class ConcreStrategyC:Strategy{	public override void AlgorithmInterface();	{		console.WriteLine("算法C实现");	}}class Context{	Strategy strategy;	public Context(Strategy strategy)	{		this.strategy=strategy;	}		public void ContexInterface()	{		strategy.AlgorithmInterface();		}}public void Main(string[] args){	Context context;		context =new Context(new ConcreStrategyA());	context.ContexInterface();		context =new Context(new ConcreStrategyB());	context.ContexInterface();		context =new Context(new ConcreStrategyC());	context.ContexInterface();		Console.Read();	}