简单工厂模式

实现一个计算机的功能，可以对两个数进行加、减、剩、除

1、创建一个运算类，让具体的运算去继承

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;
       }
    }

2、具体的操作类去继承操作类

   //加法类
   class OperAdd : Operation
   {
       public override double GetResult()
       {
           double result = 0;
           result = NumberA + NumberB;
           return result;
       }
   }

  //减法类
   class OperSub : Operation
   {
       public override double GetResult()
       {
           double result = 0;
           result = NumberA - NumberB;
           return result;
       }
   }

    //剩法类
   class OperMul : Operation 
   {
       public override double GetResult()
       {
           double result = 0;
           result = NumberA * NumberB;
           return result;
       }       
   }

    //除法类
   class OperDiv : Operation
   {
       public override double GetResult()
       {
           double result = 0;
           return result = NumberA / NumberB;
       }
   }

3、简单工厂类，里面有一个创建运算类的方法

//运算工厂类
     public class OperationFactory
    {
    //创建具体类的静态方法
      public static Operation CreateOperation(string str){
          Operation oper = null;
          switch (str) 
          {
              case "+": 
                  oper = new OperAdd(); 
                  break;
              case "-": 
                  oper = new OperSub(); 
                  break;
              case "*": 
                 oper = new OperMul(); 
                  break;
              case "/": 
                 oper = new OperDiv();
                  break;
          
          }
          return oper;
     } 
    }

3、客户端代码

 static void Main(string[] args)
        {
            // 直接通过简单工厂创建运算类
            Operation oper = OperationFactory.CreateOperation("+");
            oper.NumberA = 8;
            oper.NumberB = 10;
            oper.GetResult();
        }