Multiple IEnumerable implementations paradox

Question

1. I have a generic class A<T>, that implements IEnumerable<T[]>.

2. I want to have a convenience wrapper B that inherits from A<c

Answer 1

The difference is the following:

foreach actually looks for a public method called GetEnumerator. It doesn't really care for IEnumerable<T>. Your class B only has one public method named GetEnumerator: The one defined in B which hides the one defined in A.

ToArray on the other hand is an extension method on IEnumerable<T>. As your class is both IEnumerable<string> and IEnumerable<char[]> the call is ambiguous between the two generic arguments string and char[].

Answer 2

foreach loop does not use IEnumerable or IEnumerable<T> implementation. You can use foreach even if your class doesn't implement any of them. The only thing it needs is GetEnumerator method that returns IEnumerator implementation.

Check this question: How is foreach implemented in C#?

That's why your class works with foreach and doesn't with ToArray().