How to: Enumerate directories and files

Enumerable collections provide better performance than arrays when you work with large collections of directories and files. To enumerate directories and files, use methods that return an enumerable collection of directory or file names, or their DirectoryInfo, FileInfo, or FileSystemInfo objects.

If you want to search and return only the names of directories or files, use the enumeration methods of the Directory class. If you want to search and return other properties of directories or files, use the DirectoryInfo and FileSystemInfo classes.

You can use enumerable collections from these methods as the IEnumerable<T> parameter for constructors of collection classes like List<T>.

The following table summarizes the methods that return enumerable collections of files and directories:

Examples: Use the Directory class

The following example uses the Directory.EnumerateDirectories(String) method to get a list of the top-level directory names in a specified path.

using System;
using System.Collections.Generic;
using System.IO;

class Program
{
 private static void Main(string[] args)
 {
 try
 {
 // Set a variable to the My Documents path.
 string docPath = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);

 List<string> dirs = new List<string>(Directory.EnumerateDirectories(docPath));

 foreach (var dir in dirs)
 {
 Console.WriteLine($"{dir.Substring(dir.LastIndexOf(Path.DirectorySeparatorChar) + 1)}");
 }
 Console.WriteLine($"{dirs.Count} directories found.");
 }
 catch (UnauthorizedAccessException ex)
 {
 Console.WriteLine(ex.Message);
 }
 catch (PathTooLongException ex)
 {
 Console.WriteLine(ex.Message);
 }
 }
}

Imports System.Collections.Generic
Imports System.IO

Module Module1

 Sub Main()
 Try
 Dim dirPath As String = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments)

 Dim dirs As List(Of String) = New List(Of String)(Directory.EnumerateDirectories(dirPath))

 For Each folder In dirs
 Console.WriteLine($"{dir.Substring(dir.LastIndexOf(Path.DirectorySeparatorChar) + 1)}")
 Next
 Console.WriteLine($"{dirs.Count} directories found.")
 Catch ex As UnauthorizedAccessException
 Console.WriteLine(ex.Message)
 Catch ex As PathTooLongException
 Console.WriteLine(ex.Message)
 End Try

 End Sub
End Module

The following example uses the Directory.EnumerateFiles(String, String, SearchOption) method to recursively enumerate all file names in a directory and subdirectories that match a certain pattern. It then reads each line of each file and displays the lines that contain a specified string, with their filenames and paths.

using System;
using System.IO;
using System.Linq;

class Program
{
 static void Main(string[] args)
 {
 try
 {
 // Set a variable to the My Documents path.
 string docPath =
 Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);

 var files = from file in Directory.EnumerateFiles(docPath, "*.txt", SearchOption.AllDirectories)
 from line in File.ReadLines(file)
 where line.Contains("Microsoft")
 select new
 {
 File = file,
 Line = line
 };

 foreach (var f in files)
 {
 Console.WriteLine($"{f.File}\t{f.Line}");
 }
 Console.WriteLine($"{files.Count().ToString()} files found.");
 }
 catch (UnauthorizedAccessException uAEx)
 {
 Console.WriteLine(uAEx.Message);
 }
 catch (PathTooLongException pathEx)
 {
 Console.WriteLine(pathEx.Message);
 }
 }
}

Imports System.IO
Imports System.Xml.Linq

Module Module1

 Sub Main()
 Try
 Dim docPath As String = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments)
 Dim files = From chkFile In Directory.EnumerateFiles(docPath, "*.txt", SearchOption.AllDirectories)
 From line In File.ReadLines(chkFile)
 Where line.Contains("Microsoft")
 Select New With {.curFile = chkFile, .curLine = line}

 For Each f In files
 Console.WriteLine($"{f.File}\t{f.Line}")
 Next
 Console.WriteLine($"{files.Count} files found.")
 Catch uAEx As UnauthorizedAccessException
 Console.WriteLine(uAEx.Message)
 Catch pathEx As PathTooLongException
 Console.WriteLine(pathEx.Message)
 End Try
 End Sub
End Module

Examples: Use the DirectoryInfo class

The following example uses the DirectoryInfo.EnumerateDirectories method to list a collection of top-level directories whose CreationTimeUtc is earlier than a certain DateTime value.

using System;
using System.IO;

namespace EnumDir
{
 class Program
 {
 static void Main(string[] args)
 {
 // Set a variable to the Documents path.
 string docPath = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);

 DirectoryInfo dirPrograms = new DirectoryInfo(docPath);
 DateTime StartOf2009 = new DateTime(2009, 01, 01);

 var dirs = from dir in dirPrograms.EnumerateDirectories()
 where dir.CreationTimeUtc > StartOf2009
 select new
 {
 ProgDir = dir,
 };

 foreach (var di in dirs)
 {
 Console.WriteLine($"{di.ProgDir.Name}");
 }
 }
 }
}
// </Snippet1>

Imports System.IO

Module Module1

 Sub Main()

 Dim dirPath As String = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments)
 Dim dirPrograms As New DirectoryInfo(dirPath)
 Dim StartOf2009 As New DateTime(2009, 1, 1)

 Dim dirs = From dir In dirPrograms.EnumerateDirectories()
 Where dir.CreationTimeUtc > StartOf2009

 For Each di As DirectoryInfo In dirs
 Console.WriteLine("{0}", di.Name)
 Next

 End Sub

End Module

The following example uses the DirectoryInfo.EnumerateFiles method to list all files whose Length exceeds 10MB. This example first enumerates the top-level directories, to catch possible unauthorized access exceptions, and then enumerates the files.

using System;
using System.IO;

class Program
{
 static void Main(string[] args)
 {
 // Set a variable to the My Documents path.
 string docPath = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);

 DirectoryInfo diTop = new DirectoryInfo(docPath);

 try
 {
 foreach (var fi in diTop.EnumerateFiles())
 {
 try
 {
 // Display each file over 10 MB;
 if (fi.Length > 10000000)
 {
 Console.WriteLine($"{fi.FullName}\t\t{fi.Length.ToString("N0")}");
 }
 }
 catch (UnauthorizedAccessException unAuthTop)
 {
 Console.WriteLine($"{unAuthTop.Message}");
 }
 }

 foreach (var di in diTop.EnumerateDirectories("*"))
 {
 try
 {
 foreach (var fi in di.EnumerateFiles("*", SearchOption.AllDirectories))
 {
 try
 {
 // Display each file over 10 MB;
 if (fi.Length > 10000000)
 {
 Console.WriteLine($"{fi.FullName}\t\t{fi.Length.ToString("N0")}");
 }
 }
 catch (UnauthorizedAccessException unAuthFile)
 {
 Console.WriteLine($"unAuthFile: {unAuthFile.Message}");
 }
 }
 }
 catch (UnauthorizedAccessException unAuthSubDir)
 {
 Console.WriteLine($"unAuthSubDir: {unAuthSubDir.Message}");
 }
 }
 }
 catch (DirectoryNotFoundException dirNotFound)
 {
 Console.WriteLine($"{dirNotFound.Message}");
 }
 catch (UnauthorizedAccessException unAuthDir)
 {
 Console.WriteLine($"unAuthDir: {unAuthDir.Message}");
 }
 catch (PathTooLongException longPath)
 {
 Console.WriteLine($"{longPath.Message}");
 }
 }
}

Imports System.IO

Class Program
 Public Shared Sub Main(ByVal args As String())
 Dim dirPath As String = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments)
 Dim diTop As New DirectoryInfo(dirPath)
 Try
 For Each fi In diTop.EnumerateFiles()
 Try
 ' Display each file over 10 MB;
 If fi.Length > 10000000 Then
 Console.WriteLine("{0}" & vbTab & vbTab & "{1}", fi.FullName, fi.Length.ToString("N0"))
 End If
 Catch unAuthTop As UnauthorizedAccessException
 Console.WriteLine($"{unAuthTop.Message}")
 End Try
 Next

 For Each di In diTop.EnumerateDirectories("*")
 Try
 For Each fi In di.EnumerateFiles("*", SearchOption.AllDirectories)
 Try
 ' // Display each file over 10 MB;
 If fi.Length > 10000000 Then
 Console.WriteLine("{0}" & vbTab &
 vbTab & "{1}", fi.FullName, fi.Length.ToString("N0"))
 End If
 Catch unAuthFile As UnauthorizedAccessException
 Console.WriteLine($"unAuthFile: {unAuthFile.Message}")
 End Try
 Next
 Catch unAuthSubDir As UnauthorizedAccessException
 Console.WriteLine($"unAuthSubDir: {unAuthSubDir.Message}")
 End Try
 Next
 Catch dirNotFound As DirectoryNotFoundException
 Console.WriteLine($"{dirNotFound.Message}")
 Catch unAuthDir As UnauthorizedAccessException
 Console.WriteLine($"unAuthDir: {unAuthDir.Message}")
 Catch longPath As PathTooLongException
 Console.WriteLine($"{longPath.Message}")
 End Try
 End Sub
End Class

See also

• File and stream I/O