var fs = new FileSystem();
//with extension
var current = fs.CurrentDirectory();
//without extension
var current =  fs.DirectoryInfo.FromDirectoryName(fs.Directory.GetCurrentDirectory());

var current = new FileSystem().CurrentDirectory();
//create a "temp" subdirectory with extension
current.SubDirectory("temp").Create();
//create a "temp" subdirectory without extension
current.FileSystem.DirectoryInfo.FromDirectoryName(current.FileSystem.Path.Combine(current.FullName, "temp")).Create();

var current = new FileSystem().CurrentDirectory();
//create a "test.txt" file with extension
using (var stream = current.File("test.txt").Create())
    stream.Dispose();
//create a "test.txt" file without extension
using (var stream = current.FileSystem.FileInfo.FromFileName(current.FileSystem.Path.Combine(current.FullName, "test.txt")).Create())
    stream.Dispose();

var fs = new FileSystem();
//with extension
using (fs.CreateDisposableDirectory(out IDirectoryInfo dir))
{
    Console.WriteLine($"This directory will be deleted when control leaves the using block: '{dir.FullName}'");
}
//without extension
var temp = fs.Path.GetTempPath();
var fileName = fs.Path.GetRandomFileName();
var path = fs.Path.Combine(temp, fileName);
try
{
    IDirectoryInfo dir = fs.Directory.CreateDirectory(path);
    Console.WriteLine($"This directory will be deleted in the finally block: '{dir.FullName}'");
}
finally
{
    fs.Directory.Delete(path, recursive: true);
}

var fs = new FileSystem();
var current = fs.CurrentDirectory();
//source
var source =  current.SubDirectory("source");
source.Create(); //make sure the source directory exists
//destination
var dest = current.SubDirectory("destination");
//copy
source.CopyTo(dest, recursive: true);