File System C#

using System.IO;

List all files in directory, ignore subdirectories

foreach (var filePath in Directory.GetFiles("/path/to/directory/"))
{
    Console.WriteLine(filePath);
}

List all files in directory and subdirectories

foreach (var filePath in Directory.GetFiles("/path/to/directory/",
                                            "*",
                                            SearchOption.AllDirectories))
{
    Console.WriteLine(filePath);
}

Create directory if directory doesn’t exist

Directory.CreateDirectory("/path/to/directory/");

Check last modified time of file

var lastWrite = File.GetLastWriteTimeUtc("/path/to/file");