Question

I have a function which returns a variable number of elements, should I return an array or a List? The “collection’s” size does not change once returned, ie for all purposes the collection is immutable. I would think to just return an array, but some people have said to not return variable sized arrays from a function as it is “poor form”. Not sure why?

Does it matter that this needs to be .NET 2.0 compliant?

Answer 1

It’s bad form to return arrays if not needed, and especially to return List<T>.

Usually, you’ll want to return IEnumerable<T> or IList<T>.

If your user is going to just need to run through each element, IEnumerable<T> will provide this capability. It also allows you to potentially implement the routine (now or later) using deferred execution.

If your user needs to access elements by index, return IList<T>. This provides all of the benefits of arrays, but gives you more flexibility in your implementation. You can implement it as an array, a list, or some other collection that implements IList<T>, and you don’t have to convert/copy to an array.