第一章 （2）工厂模式

工厂模式的优势：能承受更多的扩展，只要是类似的功能就可以进行扩。即添加具体类，并在工厂中添加调用新加的类的条件即可

1.首先建立抽象类，建立各个具体功能类，建立生成工厂，文件结构图如下。

2.各个文件代码

2.1 Operation代码（抽象类）

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

namespace Calculate.Calculate
{
    class Operation
    {
        private double _numberA = 0d;
        private double _numberB = 0d;
        private double _result = 0d;

        

        public double NumberA
        {
            get { return _numberA; }
            set { _numberA = value; }
        }
        public double NumberB
        {
            get { return _numberB; }
            set { _numberB = value; }
        }
        public double Result
        {
            get { return _result; }
            set { _result = value; }
        }

        public virtual double getResult()
        {
            double result = 0d;
            return result;
        }


    }
}

2.2 OperationAdd代码（加法类）

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

namespace Calculate.Calculate
{
    class OperationAdd:Operation
    {
        public override double getResult()
        {
            Result = NumberA + NumberB;
            return Result;
        }
    }
}

2.3 OperationSub代码（减法类）

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

namespace Calculate.Calculate
{
    class OperationSub : Operation
    {
        public override double getResult()
        {
            Result = NumberA - NumberB;
            return Result;
        }
    }
}

2.4 OperationMul代码（乘法类）

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

namespace Calculate.Calculate
{
    class OperationMul : Operation
    {
        public override double getResult()
        {
            Result = NumberA * NumberB;
            return Result;
        }
    }
}

2.4 OperationDiv代码（除法类）

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

namespace Calculate.Calculate
{
    class OperationDiv : Operation
    {
        public override double getResult()
        {
            if (NumberB!=0)
            {

                Result = NumberA / NumberB;
            }
            else
            {
                Result = -1;
            }
            return Result;
        }
    }
}