简单工厂模式的实现

 该代码实现了四则运算,用简单工厂模式开发.

  class Program
    ...{
        static void Main(string[] args)
        ...{
            Console.Write("请输入数字A：");
            string A = Console.ReadLine();
            Console.Write("请选择运算符号(+、-、*、/)：");
            string B = Console.ReadLine();
            Console.Write("请输入数字B：");
            string C = Console.ReadLine();
            string D = "";
            Operation oper = OperationFactory.createOpertion(B);
            oper.NumberA = int.Parse(A);
            oper.NumberB = int.Parse(C);
            D = oper.GetResult().ToString();
            Console.WriteLine("结果是：" + D);
        }
    }

  public  class Operation
...{
    private double _numberA = 0;
    private double _numberB = 0;

    /**//// <summary>
    /// 数字A
    /// </summary>
    public double NumberA
    ...{
        get ...{ return _numberA; }
        set ...{ _numberA = value; }
    }

    /**//// <summary>
    /// 数字B
    /// </summary>
    public double NumberB
    ...{
        get ...{ return _numberB; }
        set ...{ _numberB = value; }
    }

    /**//// <summary>
    /// 得到运算结果
    /// </summary>
    /// <returns></returns>
    public virtual double GetResult()
    ...{
        double result = 0;
        return result;
    }
    }

    /**//// <summary>
    /// 加法类
    /// </summary>
    public class OperationAdd : Operation
    ...{
        public override double GetResult()
        ...{
            return this.NumberA + NumberB;
        }
    }

    /**//// <summary>
    /// 减法类
    /// </summary>
    public class OperationSub : Operation
    ...{
        public override double GetResult()
        ...{
            return NumberA - NumberB;
        }
    }

    /**//// <summary>
    /// 乘法类
    /// </summary>
    public class OperationNul : Operation 
    ...{
        public override double GetResult()
        ...{
            return NumberA * NumberB;
            //return base.GetResult();
        }
    }

    /**//// <summary>
    /// 除法类
    /// </summary>
    public class OperationDiv : Operation
    ...{
        public override double GetResult()
        ...{
            if (NumberB == 0) 
            ...{
                return 0;
            }
            return NumberA / NumberB;
            //return base.GetResult();
        }
    }

    public class OperationFactory 
    ...{
        public static Operation createOpertion(string operte)
        ...{
            Operation Oper=null;
            switch (operte)
            ...{
                case "+":
                    ...{
                        Oper = new OperationAdd();
                        break;
                    }
                case "-":
                    ...{
                        Oper = new OperationSub();
                        break;
                    }
                case "*":
                    ...{
                        Oper = new OperationNul();
                        break;
                    }
                case "/":
                    ...{
                        Oper = new OperationDiv();
                        break;
                    }
            }
                    return Oper;
        } 
    }