简单工厂

namespace 简单工厂
{
    class Program
    {
        static void Main(string[] args)
        {
            Operation oper;
            string operation = string.Empty;
            Console.WriteLine("请输入第一个数：");
            double numA = double.Parse(Console.ReadLine());
            Console.WriteLine("请输入第二个数：");
            double numB = double.Parse(Console.ReadLine());
            Console.WriteLine("请输入运算符号（+ - * /）：");
            operation = Console.ReadLine();
            oper = OperationFactory.createOperate(operation);
            oper.NumberA = numA;
            oper.NumberB = numB;
            double result = oper.GetResult();
            Console.WriteLine("结果为："+result);
            Console.ReadKey();
        }
    }

    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;
                default:
                    break;
            }
            return oper;
        }
    }
    public class Operation
    {
        private double _numberA = 0;
        private double _numberB = 0;
        public double NumberA
        {
            get { return _numberA; }
            set { _numberA = value; }
        }
        public double NumberB
        {
            get { return _numberB; }
            set { _numberB = value; }
        }
        public virtual double GetResult()
        {
            double result = 0;
            return result;
        }
    }
    class OperationAdd : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = NumberA + NumberB;
            return result;
        }
    }
    class OperationSub : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = NumberA - NumberB;
            return result;
        }
    }
    class OperationMul : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = NumberA * NumberB;
            return result;
        }
    }
    class OperationDiv : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            if (NumberB == 0)
            {
                throw new Exception("除数不能为0");
            }
            return result = NumberA / NumberB;
        }
    }

}