using System;using System.Collections.Generic;using System.Text;

namespace ConsoleApplication4{publicabstractclass Book    {publicvoid Introduce()        {            Console.WriteLine("I'm book");        }

publicvoid SayHi()        {            Console.WriteLine("Hi, I'm book");        }    }

publicclass JavaBook : Book    {// 显式加上new，跟不加new实际效果一样，只是加new之后会消除compile warningpublicnewvoid SayHi()        {            Console.WriteLine("Hi, I'm Java");        }    }

publicclass test    {public test()        {            JavaBook javaBook =new JavaBook();            Book book =new JavaBook();

            javaBook.Introduce();       //将调用JavaBook中Introduce()            javaBook.SayHi();           //将调用JavaBook中SayHi()

            book.Introduce();       //将调用Book中Introduce()            book.SayHi();           //将调用Book中SayHi()        }publicstaticvoid Main()        {            test t =new test();        }    }}

using System;using System.Collections.Generic;using System.Text;

namespace ConsoleApplication3{publicabstractclass Book    {//抽象方法，不含主体，抽象方法所在类必须为抽象类，派生类必须实现该方法publicabstractvoid Introduce();    }

publicclass JavaBook : Book    {//实现抽象方法，必须实现，注意!必须添加override关键字publicoverridevoid Introduce()        {            Console.WriteLine("I'm Java");        }    }

publicclass test    {public test()        {            JavaBook javaBook =new JavaBook();            javaBook.Introduce();      //将调用JavaBook中Introduce()            Book book =new JavaBook();            book.Introduce();      //将调用JavaBook中Introduce()        }publicstaticvoid Main()        {            test t =new test();        }    }}

using System;using System.Collections.Generic;using System.Text;

namespace ConsoleApplication2{publicabstractclass Book    {publicvirtualvoid Introduce()        {            Console.WriteLine("I'm book");        }

publicvirtualvoid SayHi()        {            Console.WriteLine("Hi, I'm book");        }    }

publicclass JavaBook : Book    {publicoverridevoid Introduce()        {            Console.WriteLine("I'm Java");        }

//注意，此方法没有override父类的方法publicvoid SayHi()        {            Console.WriteLine("Hi, I'm Java");        }    }

publicclass test    {public test()        {            JavaBook javaBook =new JavaBook();            Book book =new JavaBook();            javaBook.Introduce();       //将调用JavaBook中Introduce()            book.Introduce();       //将调用JavaBook中Introduce()

            javaBook.SayHi();      //将调用JavaBook中SayHi()            book.SayHi();           //将调用Book中SayHi()        }

publicstaticvoid Main()        {            test t =new test();        }    }}