Faster way to access the last and the first element of a List<int>

Question

The language I use is C#.

Let

List<int> numbers = new List<int>();

be a list of integers, that we want to use them to do some calculations. Is it faster to access the first element of the list as

numbers[0]

or as

numbers.First()

Also, if we want to access the last element of the list it is faster to access it as

numbers[numbers.Count-1]

or as

numbers.Last()

Answer 1

IEnumerable<T> extensions check type of source when you do First() or Last(). If source is IList<T> then indexing is used:

IList<TSource> list = source as IList<TSource>;
if (list != null)
{
    if (list.Count > 0)
    {
        return list[0];
    }
}

So, enumerator will not be created and performance will be almost same. But simple indexing will be of course faster.

Answer 2

The index-based accesses (numbers[0] and numbers[numbers.Count - 1], respectively) are probably faster by a very minimal degree, as First() and Last() require the additional method calls of the extension methods First() and Last() before accessing the list items (based on their index, again).