六、创建型模式之简单工厂模式-----《大话设计模式》

    // 运算类
    public class Operation
    {
        private double _numberA = 0;
        private double _numberB = 0;
        
        // 数字A属性     

        public double NumberA
        {
            get
            {
                return _numberA;
            }
            set
            {
                _numberA = value;
            }
        }

        // 数字B属性
        public double NumberB
        {
            get
            {
                return _numberB;
            }
            set
            {
                _numberB = value;
            }
        }

        // 得到运算结果
        public virtual double getResult()
        {
            double result = 0; 
            return result;
        }       
    }

// 加法类
    class OperationAdd : Operation
    {
        public override double getResult()
        {
            double result = 0; 
            result = NumberA + NumberB;
            return result;
        }
    }

    // 减法类
    class OperationSub : Operation
    {
       public override double getResult()
        {
            double result = 0;
            result = NumberA - NumberB;
            return result;
        }
    }

    // 乘法类
    class OperationMul : Operation
    {
        public override double getResult()
        {
            double result = 0;
            result = NumberA * NumberB;
            return result;
        }
    }

    // 除法类
    class OperationDiv : Operation
    {
        public override double getResult()
        {
            double result = 0;
            if (NumberB==0)
                throw new Exception("除数不能为0。");
            result = NumberA / NumberB;
            return result;
        }
    }

   // 简单类工厂
    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;
        }
    }

//控制台调用
static void Main(string[] args)
        {
            try
            {
                Console.Write("请输入数字A：");
                string strNumberA = Console.ReadLine();
                Console.Write("请选择运算符号(+、-、*、/)：");
                string strOperate = Console.ReadLine();
                Console.Write("请输入数字B：");
                string strNumberB = Console.ReadLine();
                string strResult = "";

                Operation oper;                                         //声明运算类
                oper = OperationFactory.createOperate(strOperate);      //根据运算符调用工厂类初始化相应运算子类
                oper.NumberA = Convert.ToDouble(strNumberA);
                oper.NumberB = Convert.ToDouble(strNumberB);
                strResult = oper.GetResult().ToString();

                Console.WriteLine("结果是：" + strResult);

                Console.ReadLine();


            }
            catch (Exception ex)
            {
                Console.WriteLine("您的输入有错：" + ex.Message);
            }
        }