Resticting访问方法对只读属性要求 [英] Resticting access to method calls on read-only properties

问题描述

我有一个类定义了一个只读属性，有效地公开了私人领域，是这样的：

I have a class that defines a read-only property that effectively exposes a private field, something like this:

public class Container
{
    private List<int> _myList;

    public List<int> MyList
    {
    	get { return _myList;}
    }

    public Container() : base ()
    {
    	_myList = new List<int>();
    }

    // some method that need to access _myList
    public SomeMethod(int x)
    {
         _myList.Add(x);
    }
}

现在这是不可能的，为消费者直接管理我的财产，所以这样的代码aContainer.MyList =新名单（）;产生一个编译时错误。
然而，消费者是绝对自由调用各种关于他得到了参考方法，所以这是完全合法的代码

now it's impossible for the consumer to manage my property directly, so code like aContainer.MyList = new List(); generates a compile-time error. However, the consumer is absolutely free to call all sorts of methods on the reference he got, so this is perfectly valid code

Container c = new Container();  
Console.WriteLine(c.MyList.Count);  
c.MyList.Add(4);  
Console.WriteLine(c.MyList.Count);

哪种击败了整个只读的概念。

which kind of defeats the whole read-only concept.

有任何理智的解决办法，这将使我有一个真正的只读引用属性格式？

Is there any sane workaround that would enable me to have a real read-only reference propery?

PS我不能只返回列表的副本，因为这时用户会认为他做了所有必要的修改，但很可惜......他们将不复存在。

P.S. I cannot just return a copy of the list because then the user will think that he made all the changes necessary, but alas... they will be gone.

推荐答案

该参考只读 ，在实际的对象。即你不能替换另一个对象的引用。所以，如果你有打破它像这样的类：

The reference is "readonly", the the actual object. I.e. you can't replace the reference with another object. So if you have a class that breaks it like this:

public class Container
{
    private readonly  List<int> _myList;

    public List<int> MyList
    {
        get { return _myList;}
    }

    public Container() : base ()
    {
        _myList = new List<int>();
    }

    public void BreakReadOnly()
    {
        _myList = new List<int>();
    }
}

...那么它甚至不会编译。这是因为一个只读域不能与任何其他对象进行重新分配。在这种情况下 BreakReadOnly 将尝试分配一个新的列表。

…then it won't even compile. It's because a readonly field can't be reassigned with any other object. In this case BreakReadOnly will try to assign a new list.

如果你真的想它的只读集合，那么你可以做这样的：

If you really want a readonly collection of it then you can do it like this:

    public ReadOnlyCollection<int> MyList
    {
        get { return _myList.AsReadOnly(); }
    }

希望这有助于。

Hope this helps.

更新：不再使用的IEnumerable的。

Updated: Removed use of IEnumerable.

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