为什么HashSet的＆LT; T＆GT;没有实现IReadOnlyCollection＆LT; T＆GT;？LT、HashSet、IReadOnlyCollection、GT
我刚刚发现，.NET Fx的，现在有3个有用的界面：
IReadOnlyCollection<T> IReadOnlyList＆LT; T＆GT;
IReadOnlyDictionary<K,V>
和我有点困惑，为什么HashSet<T>不执行 IReadOnlyCollection＆LT; T＆GT; ？是否有任何理由，或微软刚刚忘了套了吗？
UPD
在两小时google搜索，我发现有很多藏品BCL拥有 .Count之间财产，但不执行 IReadOnlyCollection＆LT; T＆GT ;。接口
UPD2
我发现这个职位http://social.msdn.microsoft.com/Forums/en/netfxbcl/thread/b4fb991a-3f5c-4923-93d4-7cd5c004f859和答案的 IMMO Landwerth 的he've所说的下面，其中
请问除了名单，其中其他收藏;>词典＆LT;>更新为 支持这些接口？
当然可以。事实上，我们的所有内置集合类型的已 实施IReadOnlyList＆LT;>和IReadOnlyDictionary＆LT;>。这意味着，就 可以直接通过列表中，T []或字典℃的实例;>到 API，它需要一个IReadOnly版本吧。
解决方案
在4.5版本的框架，的 的HashSet＆LT; T＆GT; 不执行 IReadOnlyCollection＆LT;出T＆GT; 。
这遗漏是在框架4.6版本解决了（上面的问题近12个月后释放的要求）。
这些更正不限于的HashSet＆LT; T＆GT; ，其他收藏品如的 堆栈＆LT; T＆GT; 和的 问答LT; T＆GT; 收到这些改进
揣测任何遗漏的原因是没有实际意义。这可能是疏忽或时间pressure但坦率地说，这是无关紧要的。我怀疑从微软开发团队甚至直接输入就有些主观，即使我们享受相关的轶事。
I've just found that .NET Fx now has 3 useful interfaces:
IReadOnlyCollection<T>
IReadOnlyList<T>
IReadOnlyDictionary<K,V>
And I'm bit confused why HashSet<T> do not implement IReadOnlyCollection<T>? Are there any reasons, or Microsoft just forgot about sets again?
UPD
After two-hours googling I've found that there are many collections in BCL which has .Count property but do not implement IReadOnlyCollection<T> interface.
UPD2
I've found this post http://social.msdn.microsoft.com/Forums/en/netfxbcl/thread/b4fb991a-3f5c-4923-93d4-7cd5c004f859 and the answer by Immo Landwerth where he've said following
Will other collections besides List<> and Dictionary<> be updated to support these interfaces?
Absolutely. In fact, all of our built-in collection types already implement IReadOnlyList<> and IReadOnlyDictionary<>. This means, you can directly pass an instance of List, T[] or Dictionary<> to an API that takes an IReadOnly-version of it.
解决方案
In version 4.5 of the framework, HashSet<T> does not implement IReadOnlyCollection<out T>.
This omission was resolved in version 4.6 of the framework (released almost 12 months after the above question was asked).
These corrections are not limited to HashSet<T>, other collections such as Stack<T> and Queue<T> have received these improvements.
Speculation on the reason for any omission is moot. It may be oversight or time pressure but frankly, it is of little consequence. I suspect that even direct input from the Microsoft Development Team would be somewhat subjective, even if we enjoy associated anecdotes.
