What is the performance of the Last() extension method for List?

Question

I really like Last() and would use it all the time for Lists. But since it seems to be defined for IEnumerable, I gu

Answer 1

You can just use Last with List without worrying :)

Enumerable.Last attempts to downcast the IEnumerable instance to IList . If this is possible, it uses the indexer and Count property.

Here is part of the implementation as Reflector sees it:

IList list = source as IList;
if (list != null)
{
    int count = list.Count;
    if (count > 0)
    {
        return list[count - 1];
    }
}