public class Person//基类,或称为父类
    {private string name;public string Name{get { return name; }set { name = value; }}private int age;public int Age{get { return age; }set { age = value; }}private char gender;public char Gender{get { return gender; }set { gender = value; }}public Person()//建议只要自己声明了无参构造方法,务必再声明一个无参构造方法.系统默认会调用无参构造方法
        {Console.WriteLine("我是父类");}public Person(string name, int age, char gender):this(){this.Name = name;this.Age = age;this.Gender = gender;}public void Say(){Console.WriteLine("我是{0},我今年{1}岁了,我是{2}生", name, age, gender);}}

 public class Teacher:Person//继承类,或称子类
    {private string course;public string Cource{set{course=value;}get{return course;}}private int yearsOfService;public int YearsOfService{set { yearsOfService = value; }get { return yearsOfService; }}public void SayHello(){Console.WriteLine("你们好,我是{0},我今年{1}岁了,教书{2}年了,我是{3}老师", Name, Age, yearsOfService, course);}public Teacher(string name,int age,char gender,string course,int yearsOfService):base( name, age, gender)//此处若没写base(name,age,gender)构造方法,便是默认调用Person的无参构造方法即base()
        {this.course = course;this.yearsOfService = yearsOfService;}}

 public class Student : Person//继承类Student
    {private int classId;public int ClassId{set { classId = value; }get { return classId; }}private string hobby;public string Hobby{set { hobby = value; }get { return hobby; }}public void SayHello(){Console.WriteLine("大家好,我是{0},我今年{1}岁了,我是{2}生,我是{3}班的,我喜欢{4}", Name, Age, Gender, classId, hobby);//包含基类的成员,加自己的成员,除了基类的私有成员外,其余成员都能访问到
        }public Student(string name,int age,char gender,int classId,string hobby):base(name,age,gender)//父类构造方法执行之后才执行
        {this.hobby = hobby;this.classId = classId;}}

class Program{static void Main(string[] args){//依次做自我介绍Person[] ps = new Person[]{new Teacher("翟群",23,'女',"c#",0),new Student("何雄军",24,'男',2,"计算机"),new Person("呵呵",23,'女')};//使用基类的引用访问不到子类的成员,所以要进行里氏转换,以访问到子类的成员for (int i = 0; i < ps.Length; i++){if (ps[i] is Teacher)//判断是否为Teacher类型对象
                {((Teacher)ps[i]).SayHello();//结果:你们好,我是翟群,我今年23岁了,,我教书0年了,我是c#老师
                }else if (ps[i] is Student){((Student)ps[i]).SayHello();//结果: 大家好,我是何雄军,我今年24岁了,我是男生,我是2班的,我喜欢计算机
                }else{ps[i].Say();//结果:我是呵呵,我今年23岁了,我是女生.
                }}//Teacher t = (Teacher)ps[2];// Teacher t = ps[2] as Teacher; as转换符等同与以下Teacher t = ps[2] is Teacher ? ((Teacher)ps[2]) : null;Console.ReadKey();}