0103-面向对象类的特性

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;

namespace _02面向对象
{
    class Program
    {
        static void Main(string[] args)
        {
            Person p=new Student();
            p.Age = -20;
            Console.WriteLine(p.Age); //年龄-20读取是会被属性保护输出为18
            p.SayHello();  //输出：我是人类
            Student s=((Student)p);
            s.SayHello();//输出：我是学生
            s.SecName = "女超人";
            s.Test();
            //创建教师对象实例
            Teacher th=new Teacher("阿程",28,'男',89,96,98);
            th.SayHi();//我叫阿程，我是男生，今年28岁
            th.ShowScore(); //我叫阿程，总成绩283，平均分94
            Teacher t = new Teacher("春老师", 18, '女');
            t.SayHi();
            Console.ReadKey(); 
        }
    }
    /*
     //面向对象的三大特性：封装、继承、多态
     new 创建对象：1、在堆中开辟内存空间 2、在堆中创建对象 3、调用对象的构造函数
     this 1、代表当前类的对象 2、显式的调用自己的构造函数
     base 1、调用父类的成员，包括调用父类的构造函数

     字段：存储数据
     属性：保护字段
     函数：描述对象的行为
     构造函数：初始化对象，给对象的属性进行赋值
     */
    class Person
    {
        private string _name;
        private int _age;
        public string Name
        {
            get { return _name; }
            set { _name = value; }
        }

        public int Age
        {
            get //属性值保护
            {
                if (_age <= 0 || _age > 160)
                {
                    return _age = 18;
                }
                return _age;
            }
            set { _age = value; }
        }

        public char Gender { get; set; }

        public void SayHello()
        {
            Console.WriteLine("我是人类");
        }
    }
    class Student:Person
    {
        public string SecName { get; set; }
        public new void  SayHello() //使用new关键字可以隐藏父类方法
        {
            Console.WriteLine("我是学生");
        }

        public void Test()
        {
            string SecName;
            SecName = "弹力女超人";
            Console.WriteLine("{0}",SecName); //局部变量
            Console.WriteLine("{0}",this.SecName); //成员变量
        }       
    }

    class Teacher:Person
    {
        public int Chinese { get; set; }
        public int Math { get; set; }
        public int English { get; set; }
        public Teacher(string name,int age,char gender,int chinese,int math,int english)
        {
            this.Name = name;
            this.Age = age;
            this.Gender = gender;
            this.Chinese = chinese;
            this.English = english;
            this.Math = math;
        }
        //以下两个构造方法通过this关键字调用本身的全参的构造方法
       public Teacher(string name,int age,char gender):this(name,age,gender,0,0,0)
        {
        }

        public Teacher(string name, int chinese, int math, int english) : this(name, 0, '\0', chinese, math, english)
        {
        }

        public void SayHi()
        {
            Console.WriteLine("我叫{0}，我是{1}生，今年{2}岁",this.Name,this.Gender,this.Age);
        }

        public void ShowScore()
        {
            Console.WriteLine("我叫{0}，总成绩{1}，平均分{2}",this.Name,
                this.Chinese+this.Math+this.English,(this.Chinese + this.Math + this.English)/3);
        }
    }
}