工厂方法（Factory Method）模式：定义一个用于创建对象的接口，让子类决定实例化哪一个类，工厂方法使一个类的实例化延迟到其子类。

工厂方法模式结构图：

工厂方法模式实现代码：

class Leifeng{	public void Sweep()	{		Console.WriteLine("扫地");	}	public void Wash()	{		Console.WriteLine("洗衣");	}	public void BuyRice()	{		Console.WriteLine("买米");	}}class Undergraduate:Leifeng{	}class Volunteer:Leifeng{	}interface IFactory{	Leifeng CreateLeiFeng();}class UndergraduateFactory:IFactory{	public Leifeng CreateLeiFeng()	{		return new Undergraduate();	}}class VolunteerFactory:IFactory{	public Leifeng CreateLeiFeng()	{		return new Volunteer();	}}IFactory factory=new UndergraduateFactory();Leifeng student=factory.CreateLeiFeng();student.BuyRice();student.Sweep();student.Wash();