static void Main()
{
Student student = new Student("3200707001", "闭敏媛")
{
PhoneNumber = "15699996666"
};
BookOrderManager bookOrderManager = new BookOrderManager();
student.SelectCourseEvent += bookOrderManager.AddBookOrder; //为事件注册处理函数；事件不能通过=赋值，必须通过+=注册（订阅）；
student.SelectCourseEvent += SmsService.InformAfterSelectCourse;
student.ShowMenu();
Read();
}
static void Main()
{
Student student = new Student("3200707001", "闭敏媛")
{
PhoneNumber = "17877778888"
};
BookOrderManager bookOrderManager = new BookOrderManager();
student.AfterSelectCourse = bookOrderManager.AddBookOrder; //委托引用指定的函数；
student.AfterSelectCourse += SmsService.InformAfterSelectCourse; //委托重载了运算符，从而引用更多函数，实现多播委托；
student.ShowMenu();
/*
* student.AfterSelectCourse(student, "JAVA"); //公有委托可被随意调用；若将委托定义为只写，虽可避免被随意调用，但将无法使用+=实现多播；
*/
Read();
}