Technically C# does derece allow functions to be outside of a class, however you could debate that static methods of a static class are functions and not methods. This is a good explanation here: stackoverflow.com/a/155655/2146952 The following example shows an implementation of the IEnumerator interface for a collection class of https://pursaklar-zirve-emlak89900.wikiexpression.com/3345059/en_iyi_tarafı_c_ienumerator_neden_kullanmalıyız