简单工厂设计模式的核心：把所有的子类当作父类来看待

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

namespace SimpleFactoryPattern
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("请输入你需要的笔记本品牌");
            //根据用户的输入返回相应的笔记本：父类
            string brand = Console.ReadLine();
            NoteBook nb = GetNoteBook(brand);
            if (nb!=null)
            {
                nb.SayHello();
            }
            else
            {
                Console.WriteLine("没有您需要笔记本");
            }
        }

        static NoteBook GetNoteBook(string brand)
        {
            NoteBook nb = null;
            switch (brand)
            {
                case "Lenove":
                    nb = new Lenovo();
                    break;
                case "Acer":
                    nb = new Acer();
                    break;
                case "IBM":
                    nb = new IBM();
                    break;
                case "Dell":
                    nb = new Dell();
                    break;
            }
            return nb;
        }
    }
    abstract class NoteBook
    {
        public abstract void SayHello(); 
    }
    class Lenovo : NoteBook
    {
        public override void SayHello()
        {
            Console.WriteLine("我是Lenovo笔记本");
        }
    }
    class Dell : NoteBook
    {
        public override void SayHello()
        {
            Console.WriteLine("我是Dell笔记本");
        }
    }
    class Acer : NoteBook
    {
        public override void SayHello()
        {
            Console.WriteLine("我是Acer笔记本");
        }
    }
    class IBM : NoteBook
    {
        public override void SayHello()
        {
            Console.WriteLine("我是IBM笔记本");
        }
    }
}