Program.cs

using System;
using System.IO;

namespace Branches.Net
{
    class Program
    {
        static void Main(string[] args)
        {
            int level = 0;

            void ListDirectoryContents(string directory)
            {
                level++;

                foreach (var dir in Directory.GetDirectories(directory))
                {
                    Console.WriteLine("{0} {1}", "|".PadRight(level * 3, '_'), Path.GetFileName(dir));
                    ListDirectoryContents(dir);
                }

                foreach (var file in Directory.GetFiles(directory))
                    Console.WriteLine("{0} {1}", "|".PadRight(level * 3, '_'), Path.GetFileName(file));

                level--;
            }

            ListDirectoryContents(Directory.GetCurrentDirectory());
        }
    }
}