问题
No one said that OrderedDictionary is having two copies of elements, one in a hashtable and other in a list, I can't find complexity measurements at MSDN for OrderedList.
thanks
回答1:
Have a look at
OrderedDictionary: A generic implementation of IOrderedDictionary
This implementation of an ordered dictionary is very good at lookup operations: the array allows O(1) lookups by index, and the hashtable allows O(1) lookups by key. However, the necessity of keeping the array synchronized with the hashtable means that insert/delete operations have the performance disadvantage of performing those operations on an array (O(n) at worst). There is also, of course, the extra memory requirement of storing both data structures. Because of these disadvantages, OrderedDictionary should only be used when insert/delete operations will be minimal and there is a need to efficiently access elements by index and/or key.
来源：https://stackoverflow.com/questions/2565455/what-is-the-complexity-of-ordereddictionary