private 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 operation = new Operation();
                switch (strOperate)
                {
                case "+":
                    operation = new OperationAdd();
                    break;

                case "-":
                    operation = new OperationSub();
                    break;

                case "*":
                    operation = new OperationMul();
                    break;

                case "/":
                    operation = new OperationDiv();
                    break;
                }

                operation.NumberA = Convert.ToDouble(strNumberA);
                operation.NumberB = Convert.ToDouble(strNumberB);
                strResult         = operation.GetResult().ToString();

                Console.WriteLine("结果是:" + strResult);
                Console.ReadLine();
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
                Console.ReadLine();
            }
        }
        private 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 operation = new Operation();
                switch (strOperate)
                {
                    case "+":
                        operation = new OperationAdd();
                        break;
                    case "-":
                        operation = new OperationSub();
                        break;
                    case "*":
                        operation = new OperationMul();
                        break;
                    case "/":
                        operation = new OperationDiv();
                        break;
                }

                operation.NumberA = Convert.ToDouble(strNumberA);
                operation.NumberB = Convert.ToDouble(strNumberB);
                strResult = operation.GetResult().ToString();

                Console.WriteLine("结果是:" + strResult);
                Console.ReadLine();
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
                Console.ReadLine();
            }
        }