C# 返回 ICollection<T> 而不是 List<T> 的真正优势是什么？
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What is the real advantage of returning ICollection<T> instead of a List<T>?
提问by Martin
I've read a couple of blog post mentioning that for public APIs we should always return ICollection (or IEnumerable) instead of List. What is the real advantage of returning ICollection instead of a List?
我读过几篇博客文章，提到对于公共 API，我们应该始终返回 ICollection（或 IEnumerable）而不是 List。返回 ICollection 而不是 List 的真正优势是什么？
Thanks!
谢谢！
Duplicate: What is the difference between List (of T) and Collection(of T)?
采纳答案by Soviut
An enumerator only returns one entity at a time as you iterate over it. This is because it uses a yield return. A collection, on the other hand, returns the entire list, requiring that the list be stored completely in memory.
当您迭代它时，枚举器一次只返回一个实体。这是因为它使用了收益回报。另一方面，集合返回整个列表，要求列表完全存储在内存中。
The short answer is that enumerators are lighter and more efficient.
简短的回答是枚举器更轻巧、更高效。
回答by ccoxtn
ICollection is just an interface, while List is a specific implementation of that interface. What if you wanted to later on use some other container besides a list? If you publicly expose an ICollection interface, you can change your internal container to something else later on - as long as the new container also implements the ICollection interface.
ICollection 只是一个接口，而 List 是该接口的具体实现。如果您以后想使用除列表之外的其他容器怎么办？如果您公开公开 ICollection 接口，您可以稍后将内部容器更改为其他内容 - 只要新容器也实现 ICollection 接口。
回答by Allain Lalonde
It gives you more freedom when choosing the Underlying data structure.
在选择底层数据结构时，它为您提供了更多的自由。
A List assumes that the implementation supports indexing, but ICollection makes no such assumption.
List 假定实现支持索引，但 ICollection 不做这样的假设。
This means that if you discover that a Set might provide better performance since ordering is irrelevant, then you're free to change your approach without affecting clients.
这意味着，如果您发现 Set 可能提供更好的性能，因为排序无关紧要，那么您可以在不影响客户的情况下自由更改您的方法。
It's basic encapsulation.
这是基本的封装。
回答by Powerlord
I would think IList would be more appropriate, but...
我认为 IList 会更合适，但是......
