一.虚方法

虚方法：

       Virtual关键字

       在继承含有虚方法类的时候，子类用override重写

 

   class Operate

    {

       private double _num1;

       private double _num2;

 

       public double Num1

       {

           get { return _num1; }

           set { _num1 = value; }

       }

       public double Num2

       {

           get { return _num2; }

           set { _num2 = value; }

       }

       虚方法声明

       public virtual double GetResult()

        {

            double result=0;

            return result;

        }

    }

虚方法的使用：

   class OperateAdd : Operate

    {

       public override double GetResult()

       {

           double result = Num1 + Num2;

           return result;

       }

    }

   class OperateSub : Operate

    {

       public override double GetResult()

       {

            double result = Num1 - Num2;

           return result;

       }

    }

   class OperateMul : Operate

    {

       public override double GetResult()

       {

           double result = Num1 * Num2;

           return result;

       }

    }

   class OperateDiv : Operate

    {

       public override double GetResult()

       {

           double result = 0;

           if (Num2 == 0)

                throw new Exception("除数不能为0！");

           result=Num1/Num2;

           return result;

       }

    }