If you .Remove() a specific item from a List<T> does it also remove the 'empty slot'?

Question

Feel free to correct my terminology, and understanding of the List if needed..

If I have a list of five items where each item has a unique ID...

[item 1]
[item 2]
[item 3]
[item 4]
[item 5]

and I remove item with ID 72 (for example) and it happens to be 3rd in the List...

will it end up like this...

[item 1]
[item 2]
[null]
[item 4]
[item 5]

or like this

[item 1]
[item 2]
[item 3]
[item 4]

where what used to be item 4 is now item 3, etc.

Please explain if you can :)

Answer 1

Second option. It behaves as a List, not as an array.

It is possible to remove an element at a particular index. The indices of previous elements at that and higher indices are decreased by 1.

Answer 2

Actually, with the implementation of System.Collections.Generic.List<T>, the underlying array that is used to store items will end up like this:

[item 1]
[item 2]
[item 4]
[item 5]
[null]

That is, without changing the size of the array, the 3rd item has been removed and the 4th and 5th items have been shifted.

Of course if you enumerate the collection the trailing nulls are omitted because the size of the collection is used to determine where to stop. (Edit: And attempts to access indicies beyond the logical end of the collection will fail.)