里式转换

1、里式转换
（1）子类可以赋值给父类
（2）如果父类中装的是子类对象，那么可以将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.

is:表示类型转换，如果能够转换成功，则返回true否则返回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null。

using System;
namespace _060_面对对象继承_06_里式转换
{
    class Program
    {
        static void Main(string[] args)
        {
            Student student = new Student();
            //1、子类可以赋值给父类：如果有一个地方需要一个父类作为参数，我们可以给一个子类代替。
            //Person person = student;
            //person.PersonSayHello();
            Person person = new Student();
            string s = string.Join("|", new string[] { "1", "2", "3", "4", "5" });//new string[]{} --> object 子类赋值给父类
            Console.WriteLine(s);
            //2、如果父类中装的是子类对象，那么可以将这个父类强转为子类对象
            //is的用法
            if (person is Student)
            {
                Student student1 = (Student)person;
                student1.StudentSayHello();
            }
            else
            {
                Console.WriteLine("转换失败");
            }
            //as的用法
            //Teacher teacher = person as Teacher;  转换失败  teacher中的值为null
            Student student2 = person as Student;
            student2.StudentSayHello();
            Console.ReadKey();
        }
    }
}
 class Person
    {
        public void PersonSayHello()
        {
            Console.WriteLine("我是父类");
        }
    }
 class Teacher:Person
    {
        public void TeacherSayHello()
        {
            Console.WriteLine("我是老师");
        }
    }
    class Student:Person
    {
        public void StudentSayHello()
        {
            Console.WriteLine("我是学生");
        }
    }

练习：

using System;
namespace _061_里式转换练习
{
    class Program
    {
        static void Main(string[] args)
        {
            Person[] person = new Person[10];
            Random r = new Random();
            for (int i = 0; i < person.Length; i++)
            {
                int rNumber = r.Next(1, 7);
                switch (rNumber)
                {
                    case 1:
                        person[i] = new Student();
                        ((Student)person[i]).StudentSayHi();
                        break;
                    case 2:
                        person[i] = new Beast();
                        ((Beast)person[i]).BeastSayHi();
                        break;
                    case 3:
                        person[i] = new Beauty();
                        ((Beauty)person[i]).BeautySayHi();
                        break;
                    case 4:
                        person[i] = new Handsome();
                        ((Handsome)person[i]).HandsomeSayHi();
                        break;
                    case 5:
                        person[i] = new Teacher();
                        ((Teacher)person[i]).TeacherSayHi();
                        break;
                    case 6:
                        person[i] = new Person();
                        person[i].PersonSayHi();
                        break;
                    default:
                        break;
                }
            }
            //for (int i = 0; i < person.Length; i++)
            //{
            //    //person[i].PersonSayHi();
            //    if(person[i] is Student)
            //    {
            //        ((Student)person[i]).StudentSayHi();
            //    }
            //    else if(person[i] is Beast)
            //    {
            //        ((Beast)person[i]).BeastSayHi();
            //    }
            //    else if (person[i] is Beauty)
            //    {
            //        ((Beauty)person[i]).BeautySayHi();
            //    }
            //    else if (person[i] is Handsome)
            //    {
            //        ((Handsome)person[i]).HandsomeSayHi();
            //    }
            //    else if (person[i] is Teacher)
            //    {
            //        ((Teacher)person[i]).TeacherSayHi();
            //    }
            //    else
            //    {
            //        person[i].PersonSayHi();
            //    }
            //}
            Console.ReadKey();
        }
    }
}
class Person
    {
        public void PersonSayHi()
        {
            Console.WriteLine("我是人类");
        }
    }
class Student:Person
    {
        public void StudentSayHi()
        {
            Console.WriteLine("我是学生");
        }
    }
    class Teacher:Person
    {
        public void TeacherSayHi()
        {
            Console.WriteLine("我是老师");
        }
    }
    class Beauty:Person
    {
        public void BeautySayHi()
        {
            Console.WriteLine("我是美女");
        }
    }
     class Handsome:Person
    {
        public void HandsomeSayHi()
        {
            Console.WriteLine("我是帅哥");
        }
    }
     class Beast:Person
    {
        public void BeastSayHi()
        {
            Console.WriteLine("我是野兽");
        }
    }