Implementing GetEnumerator in C++

Answer 1

Well you have a clue in th error message. your GetEnumerator method returns System::Collections::IEnumerator^ while there is another method to this class that returns System::Collections::Generic::IEnumerator^ , this method is probably inherited from IList class.

Try to replace the return value with System::Collections::Generic::IEnumerator^.

Answer 2

You need to use the Micro$oft specific explicit override syntax for to override both GetEnumerator() methods:

virtual System::Collections::IEnumerator^ GetEnumerator2() = System::Collections::IEnumerable::GetEnumerator
{ throw gcnew NotImplementedException(); }

virtual IEnumerator<CustomItem>^ GetEnumerator()
{ throw gcnew NotImplementedException(); }

Note that I renamed the non-generic GetEnumerator method to GetEnumerator2 then specifies that it overrides System::Collections::IEnumerable::GetEnumerator. You can find out more about explicit override in here