Directory, System.IO

The Directory type is found in System.IO. It provides methods that interact with the file system's concept of folders.

With this class, we create directories, get file lists from directories, test directories for existence, and delete directories. Directory is often used with Path.

EnumerateFiles

Many methods on the Directory type are available. We call them as static methods: to call EnumerateFiles, we can use Directory.EnumerateFiles.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        // Returns an IEnumerable<string>.
        foreach (string path in Directory.EnumerateFiles("C:\\"))
        {
            Console.WriteLine(path);
        }
    }
}

Exists

If you want to be certain that a directory exists, use the Directory.Exists method. A directory could be moved or deleted at any time. So code must still handle exceptions.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        if (Directory.Exists("C:\\Users"))
        {
            Console.WriteLine("Users");
        }
        if (Directory.Exists("C:\\Losers"))
        {
            Console.WriteLine("Losers");
        }
    }
}
Users

DirectoryInfo

The DirectoryInfo is another way of accessing the Directory type functionality. We access important properties and methods on a DirectoryInfo.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        // Get info.
        DirectoryInfo info = new DirectoryInfo(@"C:\perls\");

        // Write name.
        Console.WriteLine(info.Name);

        // Write file count.
        FileInfo[] array = info.GetFiles();
        Console.WriteLine(array.Length);
    }
}
perls
5

Benchmark, EnumerateFiles

I tested the Directory.EnumerateFiles method against GetFiles(). I tested a directory with just 31 files.

using System;
using System.Diagnostics;
using System.IO;

class Program
{
    const int _max = 1000;
    static void Main()
    {
        var s1 = Stopwatch.StartNew();
        // Version 1: use EnumerateFiles.
        for (int i = 0; i < _max; i++)
        {
            foreach (string path in Directory.EnumerateFiles("C:\\"))
            {
            }

        }
        s1.Stop();
        var s2 = Stopwatch.StartNew();
        // Version 2: use GetFiles.
        for (int i = 0; i < _max; i++)
        {
            string[] paths = Directory.GetFiles("C:\\");
            foreach (string path in paths)
            {
            }
        }
        s2.Stop();
        Console.WriteLine(((double)(s1.Elapsed.TotalMilliseconds * 1000000) / _max).ToString("0.00 ns"));
        Console.WriteLine(((double)(s2.Elapsed.TotalMilliseconds * 1000000) / _max).ToString("0.00 ns"));
    }
}
69516.30 ns    EnumerateFiles
69568.30 ns    GetFiles

CreateDirectory

The Directory class helpfully provides support for creating a new directory. The CreateDirectory method makes new folders.

Size

There are many ways to sum the total size of a directory. With one approach, we call GetFiles and loop through all the file names. We use the FileInfo type on each file name.

Exception

One exception that can be thrown is DirectoryNotFoundException. If you call Directory.GetFiles, and the Directory does not exist, this exception will be provoked.

GetDirectoryName

The Path type provides a GetDirectoryName method. This receives a string argument and returns the directory part of that path string.

DriveInfo

A drive is a physical directory on your computer. The C drive is often the main hard drive on a Windows computer. DriveInfo helps us handle drives.

FileSystemWatcher

We can use the FileSystemWatcher type to get notifications when a file changes in a directory. Then, we can update our memory model of the file system.

A summary

For interacting with the file system and using folders, the Directory type is helpful. Other types, such as Path, help with directory-handling code.