原始碼：

using System;

namespace Inherit
{
    public class Person
    {
        public string name; //定義域
        public int age;
        virtual public void SayHello()
        { //定義方法 //virtual表示可以被子類override
            Console.WriteLine("Hello!  My name is " + name);
        }
        public void SayHello(Person another)
        {  //構造方法過載同名的sayHello方法
            Console.WriteLine("Hello," + another.name +
                "! My name is " + name);
        }
        public bool IsOlderThan(int anAge)
        { //定義方法
            bool flg;
            if (age > anAge) flg = true; else flg = false;
            return flg;
        }
        public Person(string n, int a)
        { //構造方法
            name = n;
            age = a;
        }
        public Person(string n)
        { //構造方法過載
            name = n;
            age = -1;
        }
        public Person() : this("", 0)//呼叫其他構造方法
        {
        }
    }


    public class Student : Person  //定義子類
    {
        public string school; //增加的欄位
        public int score = 0;
        public bool isGoodStudent()
        { //增加的方法
            return score >= 90;
        }
        override public void SayHello()
        { //override覆蓋父類的方法
            base.SayHello();
            Console.WriteLine("My school is " + school);
        }
        public void SayHello(Student another)
        { //增加的方法
            Console.WriteLine("Hi!");
            if (school == another.school)
                Console.WriteLine(" Shoolmates ");
        }

        public Student()
        {  //構造方法
        }
        public Student(string name, int age, string school)
            : base(name, age) //呼叫父類的構造方法
        {
            this.school = school;
        }

        public void TestThisSuper()
        {
            int a;
            a = age;      //本句與以下兩句效果相同
            a = this.age; //使用this
            a = base.age; //使用base
        }
    }
        class Program
    {
        static void Main(string[] args)
        {
            Person p = new Person("Liming", 50);
            Student s = new Student("Wangqiang", 20, "PKU");
            Person p2 = new Student("Zhangyi", 18, "THU");
            Student s2 = (Student)p2; //型別轉換
        }
    }
}