关于基类中函数修饰符abstract和virtual的使用

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

namespace Computer.Qualifier
{
//关于基类中函数修饰符abstract和virtual的使用
class Program
{
static void Main(string[] args)
{
//V1
//Hint: The best way is just by sony or lenove//第一个版本V1我使用此方式

//V2
//开始为了写普通方法->简单工厂->工厂方法->抽象工厂->......
//竟然写着写着就写到多态了，多态和重载不是一个概念，重载是指同名函数的参数类型不同或者参数个数不同，与返回类型无关。
//而多态是指同名函数，不但参数类型和参数个数相同，还有返回类型也相同，只是函数的修饰符不同。
//最终决定调用基类还是子类，abstract/virtual/override/new要比上面的情况复杂。
//注释中的"//right"只是说在通常情况下使用最多的方式，“//bad”则反之。

//Hint: The best way is just by Dell or IBM//第二个版本V2，后面几篇文都是基于这个讲解，所以在这个版本我把修饰符换了

PC pc;
//pc.Name = "NA PC";
//pc = new Dell("");
pc = new Dell("Dell");
pc.Name = "OtherDell";
pc.Describe();

System.Console.WriteLine();
pc = new IBM("IBM");
pc.Name = "OtherIBM";
pc.Describe();

System.Console.WriteLine();
pc = new HP("HP");
pc.Name = "OtherHP";
pc.Describe();

System.Console.WriteLine();
pc = new Sony("Sony");
pc.Name = "OtherSony";
pc.Describe();

System.Console.WriteLine();
pc = new Lenovo("Lenovo");
pc.Name = "OtherLenovo";
pc.Describe();
}
}

abstract class PC//:Brand
{
//注意这篇文章中这里使用了protected，和后面文章中的改用成private有很大的不同
protected string name;

//public PC(string name){ } //bad, sub-class need tranfer this.name=name

public PC(string name)      //right, sub-calss needn't tranfer this.name=name
{
//this.name = "unknown";
this.name = name;
//this.name = !string.IsNullOrEmpty(name) ? name : "unknown";
}

//The super-class property(Name{get;set;}) don't use abstract,otherwise the sub-class(Dell/IBM/...) must implement Name{get;set;}
//public abstract string Name { get; set; } //bad
public virtual string Name { get; set; }    //right

//public abstract void Describe();       //right
public virtual void Describe() { System.Console.WriteLine("I am {0} personal computer of super-calss", name); }    //bad
}

class Dell : PC
{
public Dell(string name) : base(name)
{
//this.name = name; //no use tranfer
}

public override void Describe()
{
System.Console.WriteLine("I am {0} personal computer", name);
System.Console.WriteLine("I am {0} personal computer", Name);
}
}

class IBM : PC
{
protected new string name;  //No, or have to use it(要么不用，要么必须这样用),此处的成员变量(name)只能这样new基类同名成员变量

//the qualifier(override/new) don't use new, otherwise will call super-class
public override string Name { get; set; }    //right, use override, it's call sub-class

public IBM(string name) : base(name)
{
this.name = name;
}

public override void Describe()             //right, use override, it's call sub-class
{
System.Console.WriteLine("I am {0} personal computer", name);
System.Console.WriteLine("I am {0} personal computer", Name);
}
}

class HP : PC
{
protected new string name;
public override string Name { get; set; }   //right

public HP(string name) : base(name)
{
this.name = name;
}

public new void Describe()                  //bad
{
System.Console.WriteLine("I am {0} personal computer", name);
System.Console.WriteLine("I am {0} personal computer", Name);
}
}

class Sony : PC
{
protected new string name;
public new string Name { get; set; }        //bad

public Sony(string name) : base(name)
{
this.name = name;
}

public override void Describe()             //right
{
System.Console.WriteLine("I am {0} personal computer", name);
System.Console.WriteLine("I am {0} personal computer", Name);
}
}

class Lenovo : PC
{
protected new string name;
public new string Name { get; set; }        //bad

public Lenovo(string name) : base(name)
{
this.name = name;
}

public new void Describe()                  //bad
{
System.Console.WriteLine("I am {0} personal computer", name);
System.Console.WriteLine("I am {0} personal computer", Name);
}
}
}