Why would I use Enumerable.ElementAt() versus the [] operator?

Question

This seems like a silly question, but I haven't found the answer, so here it is. :)

In both cases, you will get an "out-of-range" exception if you fail to check the bounds of your collection. Is this just coding style preference?

And in case someone needs an example:

List<byte> myList = new List<byte>(){0x01, 0x02, 0x03}; byte testByte = myList.ElementAt(2); 

versus

byte testByte = myList[2]; 

Answer 1

Because Enumerable is more generic, and a collection represented by enumerable may not have an indexer.

But, if it does - don't use ElementAt() it's probably not going to be as efficient.

Answer 2

ElementAt() provides a unified interface for all enumerations in C#. I tend to use it quite often as I like the common API.

If the underlying type supports random access (ie, it supports the [] operator), then ElementAt will make use of that. So the only overhead is an extra method call (which is almost never relevant).

If the underlying type does not support random access, then ElementAt() simulates it by iterating the enumeration until it arrives at the element you care about. This can be very expensive and even have side effects sometimes.

There is also ElementAtOrDefault() which is often very handy.