ICollection充当IEnumerable [英] ICollection acting as IEnumerable

问题描述

我正在访问OrderedDictionary的Keys:

为什么这么说?:

扩展结果视图将枚举IEnumerable

Expanding the Results View will enumerate the IEnumerable

我认为已经列举了比IEnumerable更具体的内容(例如ICollection，IList等)?

I thought anything more concrete than an IEnumerable (eg ICollection, IList etc) are already enumerated?

推荐答案

List<T>同时实现IList<T>和IEnumerable<T>.从逻辑上讲，它既不能被枚举，也不能被枚举.这些界面仅定义了一个契约，您可以通过该契约与对象进行交互.

List<T> implements both IList<T> and IEnumerable<T>. Logically, it cannot be both already enumerated and not already enumerated. The interfaces only define a contract through which you can interact with the object.

重要的是实现接口的基础类型. LINQ表达式树使用延迟执行，其对象结构表示未决的LINQ操作.实现问题中的接口的基础类型知道它是否表示这样的延迟操作.

What matters is the underlying type implementing the interface. LINQ expression trees use deferred execution, with an object structure representing the pending LINQ operation(s). That underlying type, which implements the interfaces in the question, knows whether it represents such a deferred operation.

在这种情况下，基础对象确实使用了延迟执行，因此VS会提示您.

In this case, the underlying object does use deferred execution, so VS prompts you.

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