面向对象——多态（摘）

class Program
    {
        List<Book> books = new List<Book>();
        static void Main(string[] args)
        {
            
            Program p = new Program();
            p.Test();
         
        }  
        public void Test()
        {
            books.Add(new MathBook());
            books.Add(new EnglishBook());
            foreach (Book item in books)
            {
                //if (item is MathBook)
                //{
                //    ((MathBook)item).reading();
                //}
                //if (item is EnglishBook)
                //{
                //    ((EnglishBook)item).reading();
                //}
                item.reading();

            }
        } 
    }
    class Book
    {
        public virtual void reading()
        {

        }
    }
    class MathBook:Book
    {
        //public void reading()
        //{
        //    Console.WriteLine("我是数学书，被在校同学用");
        //}
        public override void reading()
        {
            Console.WriteLine("我是数学书，被在校同学用");
        }

    }

    class EnglishBook:Book
    {
        //public void reading()
        //{
        //    Console.WriteLine("我是英语书，被在校同学用");
        //}
        public override void reading()
        {
            Console.WriteLine("我是英语书，被在校同学用");
        }
    }
    //

　　感谢前辈提供  谢谢啦！