Functional Squares program

Program.cs

class Program
    {
        static void Main(string[] args)
        {
            foreach (int value in SquareOf(Integers()).Take(25))
            {
                Console.Out.WriteLine(value);
            }
        }

        private static IEnumerable<int> SquareOf(IEnumerable<int> integers)
        {
            return new SquareEnumerable(integers);
        }

        static IEnumerable<int> Integers()
        {
            return new IntegerEnumerable();
        }

        class SquareEnumerable : IEnumerable<int>
        {
            IEnumerable<int> _source;
            public SquareEnumerable(IEnumerable<int> source)
            {
                _source = source;
            }
            public IEnumerator<int> GetEnumerator()
            {
                return new SquareEnumerator(_source);
            }

            IEnumerator IEnumerable.GetEnumerator()
            {
                throw new NotImplementedException();
            }
        }

        class SquareEnumerator : IEnumerator<int>
        {
            private IEnumerator<int> _source;
            public SquareEnumerator(IEnumerable<int> source)
            {
                _source = source.GetEnumerator();
            }

            public int Current
            {
                get { return _source.Current * _source.Current; }
            }

            public void Dispose() { }

            object IEnumerator.Current
            {
                get { return Current; }
            }

            public bool MoveNext()
            {
                return _source.MoveNext();
            }

            public void Reset()
            {
                _source.Reset();
            }
        }

        class IntegerEnumerable : IEnumerable<int>
        {
            public IEnumerator<int> GetEnumerator()
            {
                return new IntegerEnumerator();
            }

            IEnumerator IEnumerable.GetEnumerator()
            {
                return new IntegerEnumerator();
            }
        }

        class IntegerEnumerator : IEnumerator<int>
        {
            private int _counter;

            public int Current
            {
                get { return _counter; }
            }

            object IEnumerator.Current
            {
                get { return _counter; }
            }

            public void Dispose() { }

            public bool MoveNext()
            {
                if (_counter == Int32.MaxValue) return false;
                _counter++;
                return true;
            }

            public void Reset()
            {
                _counter = 0;
            }
        }

        static IEnumerator<int> Integers2()
        {
            return null;
        }
    }