任何类的设计都要遵循耦合性低，避免重复。
设计模式的目的主要有3易。让项目易维护，易扩展，易复用。
易维护： 修改某个功能，只要修改最少的部分，比如某个类的方法。
易扩展： 项目本来有加减乘除功能，现在要扩展 根号，取余功能。 要尽量的少改代码。
易复用： 要让设计的方法不管在 控制台应用程序，web应用程序 还是 Winform程序都能使用。
简单工厂模式：解决了对象的创建问题
Operator.cs 定义了几个类，实现了加减功能。 其中通过OpeartorFactor 根据操作符来实例相应的对象。
using System;using System.Collections.Generic;using System.Linq;using System.Text;namespace 简单工厂模式{class Operation
{ private double _numberA = 0.0; private double _numberB = 0.0; public double NumberA {get { return _numberA; }
set { _numberA = value; }
}
public double NumberB {get { return _numberB; }
set { _numberB = value; }
}
public virtual double getResult() { double result = 0.0; return result;}
}
class OpeartionAdd : Operation
{ public override double getResult() { double result = 0.0;result = NumberA + NumberB;
return result;}
}
class OpeartionDel : Operation
{ public override double getResult() { double result = 0.0;result = NumberA - NumberB;
return result;}
}
class OperationFactory
{public static Operation createOpeartion(string operate)
{Operation oper = null;
switch (operate) {case "+":
oper = new OpeartionAdd();
break;case "-":
oper = new OpeartionDel();
break;}
return oper;}
}
}
现在想加入 乘除功能，那怎么办呢？
只要 先添加 2个类，并重写getResult()方法，然后再 工厂类中 加入 符号的判断
class OpeartionMul:Operation
class OpeartionDiv:Operation
case "*":
oper = new OpeartionMul();
break;修改后的文件
using System;using System.Collections.Generic;using System.Linq;using System.Text;namespace 简单工厂模式{class Operation
{ private double _numberA = 0.0; private double _numberB = 0.0; public double NumberA {get { return _numberA; }
set { _numberA = value; }
}
public double NumberB {get { return _numberB; }
set { _numberB = value; }
}
public virtual double getResult() { double result = 0.0; return result;}
}
class OpeartionAdd : Operation
{ public override double getResult() { double result = 0.0;result = NumberA + NumberB;
return result;}
}
class OpeartionDel : Operation
{ public override double getResult() { double result = 0.0;result = NumberA - NumberB;
return result;}
}
class OpeartionMul : Operation
{ public override double getResult() { double result = 0.0;result = NumberA * NumberB;
return result;}
}
class OpeartionDiv : Operation
{ public override double getResult() { double result = 0.0;result = NumberA / NumberB;
return result;}
}
class OperationFactory
{public static Operation createOpeartion(string operate)
{Operation oper = null;
switch (operate) {case "+":
oper = new OpeartionAdd();
break;case "-":
oper = new OpeartionDel();
break;case "*":
oper = new OpeartionMul();
break;case "/":
oper = new OpeartionDiv();
break;}
return oper;}
}
}