一、简单工厂模式之简易计算器

1、主程序代码

using System;

namespace _01简单工厂模式
{
    class Program
    {
        static void Main(string[] args)
        {
            Operation oper;     //实例化Operation对象
            oper = OperationFactory.createOperate("*");
            oper.NumberA = 4;
            oper.NumberB = 2;
            double result = oper.GetResult();   //调用运算方法

            Console.WriteLine(result);
            Console.ReadKey();
        }
    }
}

2、Operation运算类及具体的运算操作子类

using System;

namespace _01简单工厂模式
{
    /// <summary>
    ///Operation运算类
    /// </summary>
    public class Operation
    {
        private double _numberA = 0;    //待计算的数字A、B
        private double _numberB = 0;

        public double NumberA
        {
            get { return _numberA; }
            set { _numberA = value; }
        }
        public double NumberB
        {
            get { return _numberB; }
            set { _numberB = value; }
        }
        /// <summary>
        /// 计算结果的方法，虚拟方法用于子类重写
        /// </summary>
        /// <returns>数学运算后的结果</returns>
        public virtual double GetResult()
        {
            double result = 0;
            return result;
        }
    }

    /// <summary>
    /// 加减乘除类，继承运算类
    /// </summary>
    class OperationAdd : Operation  //加法类
    {
        public override double GetResult()
        {
            double result = 0;
            result = NumberA + NumberB;
            return result;
        }
    }
    class OperationSub : Operation  //减法类
    {
        public override double GetResult()
        {
            double result = 0;
            result = NumberA - NumberB;
            return result;
        }
    }
    class OperationMul : Operation  //乘法类
    {
        public override double GetResult()
        {
            double result = 0;
            result = NumberA * NumberB;
            return result;
        }
    }
    class OperationDiv : Operation  //除法类
    {
        public override double GetResult()
        {
            double result = 0;
            if (NumberB == 0)
                throw new Exception("被除数不能为0！");
            result = NumberA / NumberB;
            return result;
        }
    }
}

3、运算工厂类

namespace _01简单工厂模式
{
    /// <summary>
    /// 运算工厂类
    /// </summary>
    public class OperationFactory
    {
        public static Operation createOperate(string operate)
        {
            Operation oper = null;
            switch (operate)
            {
                case "+":
                    oper = new OperationAdd();
                    break;
                case "-":
                    oper = new OperationSub();
                    break;
                case "*":
                    oper = new OperationMul();
                    break;
                case "/":
                    oper = new OperationDiv();
                    break;
            }
            return oper;
        }
    }
}

注：本文内容是《大话设计模式》一书阅读过程复写代码！