简单工厂模式利用面向对象方式通过继承、封装、多态把程序的耦合度降低，设计模式使得程序更加灵活，容易修改，易于复用。

下面是服务器计算器代码：

复制代码 代码如下:

 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 namespace DesignModel
 {
     ///

     /// 计算器
     ///

     public class Calculator   //创建一个计算器的基类可以接受两个参数，任何算法只需重写计算结果方法即可。
     {
         private double _numberA;
         private double _numberB;
         public double NumberA
         {
             get { return this._numberA; }
             set { this._numberA = value; }
         }
         public double NumberB
         {
             get { return this._numberB; }
             set { this._numberB = value; }
         }
         public virtual double GetResult()
         {
             double result = 0;
             return result;
         }
     }
     ///

     /// 加法
     ///

     public class Add : Calculator    //每添加一种计算方式只需添加一个计算类并重写基类方法即可
     {
         public override double GetResult()
         {
             return  NumberA + NumberB;
         }
     }
     ///

     /// 减法
     ///

     public class Sub : Calculator
     {
         public override double GetResult()
         {
             return NumberA + NumberB;
         }
     }
     ///

     /// 计算器工厂
     ///

     public class CalculatorFactory
     {
         public static Calculator GetResult(string oper)
         {
             Calculator calcu = null;
             switch (oper)
             {
                 case "+":
                     calcu = new Add();
                     break;
                 case "-":
                     calcu = new Sub();
                     break;
             }
             return calcu;
         }
     }
 }

复制代码 代码如下:

  static void Main(string[] args)
         {
             Console.WriteLine("请输入数字A：");
             string numbera = Console.ReadLine();
             Console.WriteLine("请输入运算符：");
             string oper = Console.ReadLine();
             Console.WriteLine("请输入数字B：");
             string numberb = Console.ReadLine();
             Calculator c = CalculatorFactory.GetResult(oper);
             c.NumberA = Convert.ToDouble(numbera);
             c.NumberB = Convert.ToDouble(numberb);
             Console.WriteLine(string.Format("{0}{1}{2}={3}", numbera, oper, numberb, c.GetResult()));
             Console.ReadLine();
         }

基本验证没加，学习练习的同学可以自己加上

28种设计模式后续更新

复制代码 代码如下:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace DesignModel
{
    ///

    /// 计算器
    ///

    public class Calculator   //创建一个计算器的基类可以接受两个参数，任何算法只需重写计算结果方法即可。
    {
        private double _numberA;
        private double _numberB;
        public double NumberA
        {
            get { return this._numberA; }
            set { this._numberA = value; }
        }
        public double NumberB
        {
            get { return this._numberB; }
            set { this._numberB = value; }
        }
        public virtual double GetResult()
        {
            double result = 0;
            return result;
        }
    }
    ///

    /// 加法
    ///

    public class Add : Calculator    //每添加一种计算方式只需添加一个计算类并重写基类方法即可
    {
        public override double GetResult()
        {
            return  NumberA + NumberB;
        }
    }
    ///

    /// 减法
    ///

    public class Sub : Calculator
    {
        public override double GetResult()
        {
            return NumberA + NumberB;
        }
    }
    ///

    /// 计算器工厂
    ///

    public class CalculatorFactory
    {
        public static Calculator GetResult(string oper)
        {
            Calculator calcu = null;
            switch (oper)
            {
                case "+":
                    calcu = new Add();
                    break;
                case "-":
                    calcu = new Sub();
                    break;
            }
            return calcu;
        }
    }
}