工厂模式

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

namespace jisuan
{
    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");
            }
            result = NumberA / NumberB;
            return result;
        }
    }
}
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;


namespace jisuan
{
    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;
            }
            return oper;
        }
     
    }
}using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;

namespace jisuan
{
    static class Program
    {
        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1());
        }
    }
}