class Program
    {
        static void Main(string[] args)
        {
            foreach (var f in enumfiles(@"D:\\"))
            {
                Console.WriteLine(f);
            }
        }

        static IEnumerable<string> enumfiles(string dirname)
        {
            var stack = new Stack<string>();
            stack.Push(dirname);

            while (stack.Count > 0)
            {
                var present = stack.Pop();
                foreach (var f in Directory.EnumerateFiles(present, "*"))
                {
                    yield return f;
                }

                foreach (var d in Directory.EnumerateDirectories(present))
                {
                    stack.Push(d);
                }
            }
        }

    }