静态工厂模式

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace 简单工厂模式
{
//抽象类相当于接口，
//抽象方法没有实现体，子类必须实现，
//虚方法有实现体，子类可以选择性重写
public abstract class Operator
{
public int NumberA { get; set; }
public int NumberB { get; set; }

public abstract double GetResult();  //有虚方法就一定定义为抽象类

}
public class operatorAdd : Operator
{
public override double GetResult()
{
return NumberA + NumberB;
}
}
public class operatorSub : Operator
{
public override double GetResult()
{
return NumberA - NumberB;
}
}
public class operatorMul : Operator
{
public override double GetResult()
{
return NumberA * NumberB;
}
}
public class operatorDiv : Operator
{
public override double GetResult()
{
return NumberA/NumberB;
}
}
//静态工厂类，由客户端输入决定实现那个子类
class operatorFactory
{
public static Operator createOperator(string type)
{
Operator op = null;
switch (type)
{
case "+":
op=  new operatorAdd();
break;
case "-":
op =  new operatorSub();
break;
case "*":
op =  new operatorMul();
break;
case "/":
op =  new operatorDiv();
break;
}
return op;
}
}
class Program
{
static void Main(string[] args)
{
Operator operat = operatorFactory.createOperator("*");
operat.NumberA = 2;
operat.NumberB = 4;
double result = operat.GetResult();
Console.WriteLine(result);
}
}
}