Supporting "foreach" without implementing IEnumerable

Krzysztof Cwalina wrote a post detailing how have your class support the "foreach" loop without implementing the IEnumerable interface:

1. Public GetEnumerator() method that returns a type with 2 members:
2. The type will have a bool MoveMext() method.
3. The type will have an Current property of type object.

Example:

class Foo {
    public Bar GetEnumerator() { return new Bar(); }

    public struct Bar {
        public bool MoveNext() {
            return false;
        }
        public object Current {
            get { return null; }
        }
    }
}