问题
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?
Thanks!
Duplicate: What is the difference between List (of T) and Collection(of T)?
回答1:
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.
The short answer is that enumerators are lighter and more efficient.
回答2:
It gives you more freedom when choosing the Underlying data structure.
A List assumes that the implementation supports indexing, but ICollection makes no such assumption.
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.
It's basic encapsulation.
回答3:
I would think IList would be more appropriate, but...
回答4:
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.
回答5:
See What is the difference between List (of T) and Collection(of T)?
来源：https://stackoverflow.com/questions/426182/what-is-the-real-advantage-of-returning-icollectiont-instead-of-a-listt