def ThisWorks() as IEnumerable:
	yield 1
	yield 2
	yield 3
		
def ThisWont():
	yield 1
	yield 2
	yield 3


C# sees definitions as:

IEnumerable ThisWorks()
IEnumerable<int> ThisWont()


foreach(int i in f.ThisWorks())
	MessageBox.Show(i.ToString());
foreach(int i in f.ThisWont())
	MessageBox.Show(i.ToString());

'boolib.MyClass.ThisWont()' is inaccessible due to its protection level (CS0122)