C# 'as'关键字是否会返回该类的所有成员？

我做了一些测试，发现了一些奇怪的东西。 假设我有这个接口

interface IRobot
    {
         int Fuel { get; }
    }

正如你所看到的，它是只读的。现在我要创建一个实现它的类

 class FighterBot : IRobot
    {

        public int Fuel { get; set; }
    }

现在您可以阅读并设置它。让我们做一些测试：

        FighterBot fighterBot;
        IRobot robot;
        IRobot robot2;
        int Fuel;
public Form1()
        {
            InitializeComponent();
            fighterBot = new FighterBot();
            robot = new FighterBot();
        }

首先，我这样做：

 Fuel = fighterBot.Fuel;// Can get it
            fighterBot.Fuel = 10; //Can set it

 Fuel = robot.Fuel; //Can get it
            robot.Fuel = 10; //Doesn't work, is read only

这是意料之中的，然后我做了这个：

 Fuel = fighterBot.Fuel;// Can get it
            fighterBot.Fuel = 10; //Can set it

 Fuel = robot.Fuel; //Can get it
            robot.Fuel = 10; //Doesn't work, is read only

这也是意料之中的。但当我这么做的时候：

robot2 = robot as FighterBot;
            Fuel = robot2.Fuel; //Can get it
            robot2.Fuel = 10;//Doesn't work, is read only

---

为什么不起作用？它不是把机器人2当作战士吗？因此，它是否能够设置燃油？

即使您通过“as”语句将

robot

投射到

FighterBot

，您仍将结果存储在

IRobot

类型的变量中，因此

燃油

仍然是只读的

您需要将转换结果存储在类型为

FighterBot

的变量中：

var robot3 = robot as FighterBot;

---

然后它就会工作。

即使您通过“as”语句将

robot

转换为

FighterBot

，您也会将结果存储在

IRobot

类型的变量中，因此

Fuel

仍然是只读的

interface IRobot
{
     int Fuel { get; }
}

robot2 = robot as FighterBot;
Fuel = robot2.Fuel;

// robot2 is STILL stored as IRobot, so the interface allowed 
// to communicate with this object will be restricted by 
// IRobot, no matter what object you put in (as long as it implements IRobot)
robot2.Fuel = 10; // evidently, won't compile.

您需要将转换结果存储在类型为

FighterBot

的变量中：

var robot3 = robot as FighterBot;

那就行了

interface IRobot
{
     int Fuel { get; }
}

robot2 = robot as FighterBot;
Fuel = robot2.Fuel;

// robot2 is STILL stored as IRobot, so the interface allowed 
// to communicate with this object will be restricted by 
// IRobot, no matter what object you put in (as long as it implements IRobot)
robot2.Fuel = 10; // evidently, won't compile.

更多背景：

IRobot r = new FighterBot();
// you can only call method // properties that are described in IRobot

如果要与对象交互并设置属性，请使用为其设计的界面

FigherBot r = new FighterBot();
r.Fuel = 10;

更多背景：

IRobot r = new FighterBot();
// you can only call method // properties that are described in IRobot

如果要与对象交互并设置属性，请使用为其设计的界面

FigherBot r = new FighterBot();
r.Fuel = 10;

---

IRobot的燃料确实是只读的，这是正确的！如果你说

var robot3=robot as FighterBot，它就会起作用。C#编译器使用声明的变量类型来确定可用的函数；给robot2分配一个新值不会改变原来声明的类型（仍然是IRobot）。IRobot的燃料确实是只读的，这是正确的！如果你说
var robot3=robot as FighterBot，它就会起作用。C#编译器使用声明的变量类型来确定可用的函数；为robot2分配新值不会更改原始声明的类型（仍然是IRobot）。