Shouldn't there be a SortedList<T>?

[alexandrehtrb]

I was looking at SortedList and I noticed that it actually is a kind of Dictionary, the difference being that a SortedList allows duplicate and null "keys", whilst a Dictionary does not.

But for use cases where the key and the value are the same element, the SortedList uses more memory, as it allocates arrays for both keys and values. A SortedList<T> would be more efficient. Shouldn't there be one?

I was unsure of opening an issue for this, so I started as a discussion.

[huoyaoyuan]

You can actually use SortedSet<T>.

[alexandrehtrb]

SortedSet<T> doesn't allow repeated items and doesn't have indexes...

[huoyaoyuan]

In that case, List<T> with BinarySearch would be the common practice.

[tannergooding]

If you feel like there should be an explicit SortedList<T> to avoid the overhead of SortedList<T, T> or SortedList<T, byte> then feel free to open a proposal.

There's always one more collection type that could be exposed and most of them could be provided by external libraries instead. It being in the core libraries really depends on need/demand.