程序由两部分组成，如下代码所示。第一部分定义了委托、类和事件。第二部分进行验证。 

using System;
namespace HelloWorldApplication 
{ public delegate void DelegateRing();public class Bell{ public event DelegateRing Ring;public void OnRing(){ Ring(); } } / 请填写代码 / class HelloWorld { static void Main(string[] args) { try{ Teacher teacher = new Teacher(); teacher.Register(new Bell()); Student student = new Student(); student.Register(new Bell()); Console.ReadKey(); } catch(Exception ex) { Console.WriteLine(ex.Message); } } } 
}

只需要输出样例输出的结果

只需要提交需要填写的代码

    public class Teacher{public void Register(Bell bell){Console.WriteLine("teacher");}    }public class Student{public void Register(Bell bell){Console.WriteLine("student");}}