简单工厂模式

客户端代码:

        static void Main(string[] args)
        {
            Operator p = OperatorFactory.CreateOperate("+");
            Console.WriteLine(p.GetResult());
            Console.ReadLine();
        }

服务端代码:

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

namespace CalculatorProgram
{
    class Operator
    {

        public double numA
        {
            get;
            set;
        }

        public double numB
        {
            get;
            set;
        }

        public virtual double GetResult()
        {
            return 0;
        }
    }

    class AddOperator : Operator
    {
        public override double GetResult()
        {
            return numA + numB;
        }
    }

    class SubOperator : Operator
    {
        public override double GetResult()
        {
            return numA - numB;
        }
    }

    class OperatorFactory
    {
        public static Operator CreateOperate(string oper)
        {
            switch (oper)
            {
                case "+":
                    return new AddOperator();
                case "-":
                    return new SubOperator();
                default:
                    return null;
            }
        }
    }