设计模式学习1：简单工厂模式实现加减乘除等运算

　　抽象基类（也可以用接口等实现）：运算的基类

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

namespace 简单工厂模式_四则运算
{
    abstract class Operation
    {
        protected double a;
        protected double b;
        public void SetValue(double a,double b)
        {
            this.a = a;
            this.b = b;
        }
        public abstract double GetResult();
    }
}

　　派生类：加减乘除运算

1.加法

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

namespace 简单工厂模式_四则运算
{
    class Jia:Operation
    {
        public override double GetResult()
        {
            return a + b;
        }
    }
}

2.减法

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

namespace 简单工厂模式_四则运算
{
    class Jian:Operation
    {
        public override double GetResult()
        {
            return a - b;
        }
    }
}

3.乘法

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

namespace 简单工厂模式_四则运算
{
    class Cheng:Operation
    {
        public override double GetResult()
        {
            return a * b;
        }
    }
}

4.除法

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

namespace 简单工厂模式_四则运算
{
    class Chu:Operation
    {
        public override double GetResult()
        {
            if(b!=0)
            {
                return a / b;
            }
            else
            {
                throw new Exception("除数为0");
            }
        }
    }
}

5.等等。。。。

　　工厂类：

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

namespace 简单工厂模式_四则运算
{
    class FactoryOperation
    {
        
        public static Operation GetOperation(double a,double b,string operation)
        {
            Operation value = null;
            if(operation=="+")
            {
                value = new Jia();
            }
            else if(operation=="-")
            {
                value = new Jian();
            }

            else if(operation=="*")
            {
                value = new Cheng();
            }

            else if(operation=="/")
            {
                value = new Chu();
            }
            value.SetValue(a, b);
            return value;
        }
    }
}

　　主程序调用：

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

namespace 简单工厂模式_四则运算
{
    class Program
    {
        static void Main(string[] args)
        {
            var x = FactoryOperation.GetOperation(3, 0, "/");
            double result = x.GetResult();
            Console.WriteLine(result);
            Console.ReadKey();
        }
    }
}