c# 虚方法（virtual）与 多态（Polymorphism）

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
//虚方法（virtual）
//virtual 关键字用于修饰方法、属性、索引器或事件声明，并且允许在派生类中重写这些对象。
//多态（Polymorphism）
//多态是指两个或多个属于不同类的对象，对同一个消息做出不同响应的能力。
namespace 虚方法
{
    class A
    {
        public virtual void F()
        {
            Console.WriteLine("A.F");
        }
    }
    class B : A
    {
        public override void F()
        {
            Console.WriteLine("B.F");
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            B b = new B();
            A a = b;
            a.F();  //"B.F"
            b.F();  //"B.F"
            Console.ReadKey();
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace 虚方法1
{
    //员工类
    class Employee
    {
        protected string _name;
        public Employee()
        {

        }
        public Employee(string name)
        {
            _name = name;
        }

        public virtual void StartWork()  //虚方法
        {
            Console.Write(_name + "开始工作：");
        }
    }
    //经理类
    class Manager : Employee  
    {
        //public Manager(string name)
        //{
        //    base._name = name;
        //}
        //构造函数
        public Manager(string name): base(name) //赋值给基类(Employee)构造函数name
        {

        }
        //重写虚方法
        public override void StartWork()  //使用虚方法实现面向对象的多态
        {
            base.StartWork();   //调用基类的方法
            Console.WriteLine("给员工下达任务");
        }
    }
    //秘书类
    class Secretary : Employee
    {
        public Secretary(string name) : base(name) { }
        public override void StartWork()
        {
            base.StartWork();
            Console.WriteLine("协助经理");
        }
    }
    //销售类
    class Seller : Employee
    {
        public Seller(string name) : base(name) { }
        public override void StartWork()
        {
            base.StartWork();
            Console.WriteLine("销售产品");
        }
    }
    //财务类
    class Accountant : Employee
    {
        public Accountant(string name) : base(name) { }
        public override void StartWork()
        {
            base.StartWork();
            Console.WriteLine("管理公司财政");
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            Employee[] emp = new Employee[5];
            emp[0] = new Manager("张三");
            emp[1] = new Secretary("李四");
            emp[2] = new Seller("王五");
            emp[3] = new Seller("马六");
            emp[4] = new Accountant("钱七");
            Console.WriteLine("早上8点，开始工作");
            foreach (Employee e in emp)
            {
                e.StartWork();
            }
            Console.ReadKey();
        }
    }
}