[你必须知道的.NET] 第六回：深入浅出关键字---base和this

base和this示例
using System;
namespace Anytao.net.My_Must_net
{
    public class Action
    {
        public static void ToRun(Vehicle vehicle)
        {
            Console.WriteLine("{0} is running.", vehicle.ToString());
        }
    }
    public class Vehicle
    {
        private string name;
        private int speed;
        private string[] array = new string[10];

        public Vehicle()
        {
        }
        //限定被相似的名称隐藏的成员
        public Vehicle(string name, int speed)
        {
            this.name = name;
            this.speed = speed;
        }
        public virtual  void ShowResult()
        {
            Console.WriteLine("The top speed of {0} is {1}.", name, speed);
        }
        public void Run()
        {
            //传递当前实例参数
            Action.ToRun(this);
        }
        //声明索引器，必须为this，这样就可以像数组一样来索引对象
        public string  this[int param]
        {
            get{return array[param];}
            set{array[param] = value;}
        }
    }
    public class Car: Vehicle
    {
        //派生类和基类通信，以base实现，基类首先被调用
        //指定创建派生类实例时应调用的基类构造函数
        public Car()
            : base("Car", 200)
        { }

        public Car(string name, int speed)
            : this()
        { }

        public override void ShowResult()
        {
            //调用基类上已被其他方法重写的方法
            base.ShowResult();
            Console.WriteLine("It's a car's result.");
        }
    }
    public class Audi : Car
    {
        public Audi()
            : base("Audi", 300)
        { }

        public Audi(string name, int speed)
            : this()
        { 
        }
        public override void ShowResult()
        {
            //由三层继承可以看出，base只能继承其直接基类成员
            base.ShowResult();
            base.Run();
            Console.WriteLine("It's audi's result.");
        }
    }
    public class BaseThisTester
    {
        public static void Main(string[] args)
        {
            Audi audi = new Audi();
            audi[1] = "A6";
            audi[2] = "A8";
            Console.WriteLine(audi[1]);
            audi.Run();
            audi.ShowResult();
        }
    }
}

Code
.method public hidebysig virtual instance void 
        ShowResult() cil managed
{
  // 代码大小       27 (0x1b)
  .maxstack  8
  IL_0000:  nop
  IL_0001:  ldarg.0
  //base调用父类成员
  IL_0002:  call       instance void Anytao.net.My_Must_net.Car::ShowResult()
  IL_0007:  nop
  IL_0008:  ldarg.0
  //base调用父类成员，因为没有实现Car.Run(),所以指向更高级父类
  IL_0009:  call       instance void Anytao.net.My_Must_net.Vehicle::Run()
  IL_000e:  nop
  IL_000f:  ldstr      "It's audi's result."
  IL_0014:  call       void [mscorlib]System.Console::WriteLine(string)
  IL_0019:  nop
  IL_001a:  ret
} // end of method Audi::ShowResult

IL分析base和this执行
.method public hidebysig static void  Main(string[] args) cil managed
{
  .entrypoint
  // 代码大小       61 (0x3d)
  .maxstack  3
  .locals init (class Anytao.net.My_Must_net.Audi V_0)
  IL_0000:  nop
  //使用newobj指令创建新的对象，并调用构造函数初始化
  IL_0001:  newobj     instance void Anytao.net.My_Must_net.Audi::.ctor()
  IL_0006:  stloc.0
  IL_0007:  ldloc.0
  IL_0008:  ldc.i4.1
  IL_0009:  ldstr      "A6"
  IL_000e:  callvirt   instance void Anytao.net.My_Must_net.Vehicle::set_Item(int32,
                                                                              string)
  IL_0013:  nop
  IL_0014:  ldloc.0
  IL_0015:  ldc.i4.2
  IL_0016:  ldstr      "A8"
  IL_001b:  callvirt   instance void Anytao.net.My_Must_net.Vehicle::set_Item(int32,
                                                                              string)
  IL_0020:  nop
  IL_0021:  ldloc.0
  IL_0022:  ldc.i4.1
  IL_0023:  callvirt   instance string Anytao.net.My_Must_net.Vehicle::get_Item(int32)
  IL_0028:  call       void [mscorlib]System.Console::WriteLine(string)
  IL_002d:  nop
  IL_002e:  ldloc.0
  IL_002f:  callvirt   instance void Anytao.net.My_Must_net.Vehicle::Run()
  IL_0034:  nop
  IL_0035:  ldloc.0
  //base.ShowResult最终调用的是最高级父类Vehicle的方法，
  //而不是直接父类Car.ShowResult()方法，这是应该关注的
  IL_0036:  callvirt   instance void Anytao.net.My_Must_net.Vehicle::ShowResult()
  IL_003b:  nop
  IL_003c:  ret
} // end of method BaseThisTester::Main