using System;

using System.Linq;

using System.IO;

using System.Threading.Tasks;

​

public class Program

{

    public static async Task Main()

    {

        Directory.CreateDirectory("foo/bar");

        Directory.CreateDirectory("foo/empty");

        File.Create("foo/foo_file1.txt");

        File.Create("foo/bar/bar_file1.txt");

​

        var oldPath = "foo";

        var newPath = "dummy";

​

        var oldDirectory = Path.GetFullPath(oldPath);

        var oldDirectoryParent = Path.GetDirectoryName(oldDirectory);

        var newDirectory = Path.Combine(oldDirectoryParent, newPath);

        Directory.CreateDirectory(newDirectory);

​

        var paths = Directory

            .EnumerateFileSystemEntries(oldDirectory, "*.*", SearchOption.AllDirectories);

        var filesAndFolders = paths.ToLookup(Directory.Exists);

​

        var directoryTasks = filesAndFolders[true]

            .Select(path => newDirectory + path.Substring(oldDirectory.Length))

            .Select(CreateDirectoryAsync);

        await Task.WhenAll(directoryTasks);

​

        var fileTasks = filesAndFolders[false]

            .Select(path => newDirectory + path.Substring(oldDirectory.Length))

            .Select(CreateAsync);

        await Task.WhenAll(fileTasks);

​

        foreach (var entry in Directory.EnumerateFileSystemEntries(newDirectory, "*.*", SearchOption.AllDirectories))

        {

            Console.WriteLine(entry);

        }

    }

​

    public static Task<FileStream> CreateAsync(string path) => Task.Run(() => File.Create(path));

    public static Task<DirectoryInfo> CreateDirectoryAsync(string path) => Task.Run(() => Directory.CreateDirectory(path));

}