简单工厂模式

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

namespace Calculate
{
    class Program
    {
        static void Main(string[] args)
        {
            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.WriteLine("请输入数字B：");
            string strNumberB = Console.ReadLine();
            string strResult = "";
            strResult = Convert.ToString(Operation.GerResult(Convert.ToDouble(strNumberA),Convert.ToDouble(strNumberB),strOperate));
            Console.WriteLine("结果是："+strResult);
            Console.ReadLine();
        }
    }
}

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

namespace Calculate
{
   public class Operation
    {
       public static double GerResult(double numberA,double numberB,string operate) {
           double result = 0d;
           switch (operate)
           {
               case "+":
                   result = numberA + numberB;
                   break;
               case "-":
                   result = numberA - numberB;
                   break;
               case "*":
                   result = numberA * numberB;
                   break;
               case "/":
                   result = numberA / numberB;
                   break;
               default:
                   break;
           }
           return result;
       }
    }


}