Question

3 questions :

1) why does the out put is taken from the NON generic function ?

2) why do I have to implement ALSO the NON generic function ?

3) What do I need to do if i want to see the Generic function output ( the int’s) ?

Answer 1

1. The foreach keyword does not require the collection to implement IEnumerable at all; rather, it will call any defined GetEnumerator methods.

2. IEnumerable<T> implements IEnumerable for compatibility reasons.

3. You should implement IEnumerable.GetEnumerator() explicitly and have the normal method return IEnumerator<T>.

If the class has a normal GetEnumerator() method (as opposed to an explicit interface implementation), the compiler will call it.
The spec says:

• Otherwise, determine whether the type X has an appropriate GetEnumerator method:
  • Perform member lookup on the type X with identifier GetEnumerator and no type arguments. If the member lookup does not produce a match,
    or it produces an ambiguity, or produces a match that is not a method
    group, check for an enumerable interface as described below. It is
    recommended that a warning be issued if member lookup produces
    anything except a method group or no match.
  • Perform overload resolution using the resulting method group and an empty argument list. If overload resolution results in no
    applicable methods, results in an ambiguity, or results in a single
    best method but that method is either static or not public, check for
    an enumerable interface as described below. It is recommended that a
    warning be issued if overload resolution produces anything except an
    unambiguous public instance method or no applicable methods.
  • […]
• Otherwise, check for an enumerable interface: