1、里氏转换 1)、子类可以赋值给父类 2)、如果父类中装的是子类对象，那么可以讲这个父类强转为子类对象。
2、 子类对象可以调用父类中的成员，但是父类对象永远都只能调用自己的成员。
3、 is：表示类型转换，如果能够转换成功，则返回一个true，否则返回一个false as：表示类型转换，如果能够转换则返回对应的对象，否则返回一个null
4、protected 受保护的：可以在当前类的内部以及该类的子类中访问。
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace _03里氏转换练习 { class Program { static void Main(string[] args) { //创建10个对象 通过一个循环 去调用他们各自打招呼的方法 //Student s = new Student(); //Person p = new Person(); //ShuaiGuo sg = new ShuaiGuo(); Person[] pers = new Person[10]; Random r = new Random(); for (int i = 0; i < pers.Length; i++) { int rNumber = r.Next(1, 7); switch (rNumber)//1-6 { case 1: pers[i] = new Student(); break; case 2: pers[i] = new Teacher(); break; case 3: pers[i] = new ShuaiGuo(); break; case 4: pers[i] = new MeiLv(); break; case 5: pers[i] = new YeShou(); break; case 6: pers[i] = new Person(); break; } } for (int i = 0; i < pers.Length; i++) { // pers[i].PersonSayHi(); if (pers[i] is Student) { ((Student)pers[i]).StudentSayHi(); // pers[i].PersonSayHi(); } else if (pers[i] is Teacher) { ((Teacher)pers[i]).TeacherSayHi(); } else if (pers[i] is ShuaiGuo) { ((ShuaiGuo)pers[i]).ShuaiGuoSayHi(); } else if (pers[i] is YeShou) { ((YeShou)pers[i]).YeShouSayHi(); } else if (pers[i] is MeiLv) { ((MeiLv)pers[i]).MeiLvSayHi(); } else { pers[i].PersonSayHi(); } } Console.ReadKey(); } } public class Person { public void PersonSayHi() { Console.WriteLine("我是人类"); } } public class Student : Person { public void StudentSayHi() { Console.WriteLine("我是学生"); } } public class Teacher : Person { public void TeacherSayHi() { Console.WriteLine("我是老师"); } } public class MeiLv : Person { public void MeiLvSayHi() { Console.WriteLine("我是镁铝"); } } public class ShuaiGuo : Person { public void ShuaiGuoSayHi() { Console.WriteLine("我是帅锅"); } } public class YeShou : Person { public void YeShouSayHi() { Console.WriteLine("我是野兽"); } } } using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace _04protected访问修饰符 { class Program { static void Main(string[] args) { //public private Person p = new Person(); } } public class Person { protected string _name; public string Name { get { return _name; } set { _name = value; } } } public class Student : Person { public void Test() { } } }