In .NET, Array only extends IEnumerable, so will there be boxing and unboxing when a foreach loop goes through a value type array?

Question

Array only extends the non-generic version of IEnumerable, so will there be boxing and unboxing when a foreach loop goes through a value type array?

I am guessing not, because that would be lame. If my guess is right, then how does foreach go through a value type array? Does it not use the Array.GetEnumerator method? And if not, why does Array extends IEnumerable?

Thanks

Answer 1

Array has a lot of special casing in the runtime. In particular it is pseudo-generic. i.e. if you specify a concrete array type like T[] implement the generic collection interfaces like IEnumerable<T>.

If I recall correctly it even supported non boxing iteration with foreach before generics by having GetEnumerator return a concrete type with a strongly typed Current. This works since foreach does not require the IEnumerator/IEnumerable interfaces, but works with correctly named members too.

So you can iterate over arrays with foreach without boxing.