Introduction

The .NET framework has a significant limitation when it comes to accessing files. All the classes, methods and properties in the System.IO namespace that manipulates file and folder names are limited to so-called system-defined maximum lengths. From the .NET documentation:

The specified path, file name, or both exceed the system-defined maximum length. For example, on Windows-based platforms, paths must be less than 248 characters, and file names must be less than 260 characters.

This limitation does not cause problems in most situations. But on Windows systems, if there is a need to access a files whose name or path is longer than the .NET limit, a %System.IO.PathTooLongException% will be thrown.

To counter this, Xceed FileSystem implements the WindowsDiskFile and WindowsDiskFolder classes. The classes work in the exact same way as DiskFile and DiskFolder but internally, they do not use the .NET framework to access the file or folder they represent. Instead, they make direct, native calls to the Windows API. For example, to open a file for reading, WindowsDiskFile will call the CreateFile() function of the Windows API. The path limit under Windows is much larger than the .NET framework. It stands at 32,767 characters.

Usage

The WindowsDiskFile and WindowsDiskFolder classes are located in the Xceed.FileSystem.Windows assembly. To use the classes, the Xceed.FileSystem.Windows.dll file needs to be added as a reference in your application project.

Because the functionality requires calling Windows directly, using the Xceed.FileSystem.Windows assembly requires the "full trust" permission level and will only work on Windows systems.

The Xceed.FileSystem.Windows assembly is entirely optional. No Xceed assembly directly references it so existing application will continue to behave as they did before.

Namespace

The WindowsDiskFile and WindowsDiskFolder classes are located in the Xceed.FileSystem.Windows namespace. The namespace must be added to your code.

using Xceed.FileSystem;
using Xceed.FileSystem.Windows;

Imports Xceed.FileSystem
Imports Xceed.FileSystem.Windows

Long file names and paths

A path is considered long when it more than 248 characters in length. A file name is considered long when it is more than 260 characters in length.

string veryLongFileName = @"SomeLongFileNameThatGoesOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnUntilItEnds.dat";
string veryLongPath = @"Folder1\Folder2\Folder3\Folder4\Folder5\Folder6\Folder7\Folder8\Folder9\SomeLongFolderNameThatGoesOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnUntilItEnds\FinalFolder";

Private veryLongFileName As String = "SomeLongFileNameThatGoesOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnUntilItEnds.dat"
Private veryLongPath As String = "Folder1\Folder2\Folder3\Folder4\Folder5\Folder6\Folder7\Folder8\Folder9\SomeLongFolderNameThatGoesOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnAndOnUntilItEnds\FinalFolder"

Usage with normal paths

Usage of WindowsDiskFile and WindowsDiskFolder is not restricted to long paths, you can use the classes on normal paths as you would with DiskFile and DiskFolder.

AbstractFile file = new WindowsDiskFile( @"D:\Data\SomeFile.dat" );
AbstractFolder destinationFolder = new WindowsDiskFolder( @"D:\SomeFolder" );

file.CopyTo( destinationFolder, true );

Dim file As AbstractFile = New WindowsDiskFile("D:\Data\SomeFile.dat")
Dim destinationFolder As AbstractFolder = New WindowsDiskFolder("D:\SomeFolder")

file.CopyTo(destinationFolder, True)

Mixing use of DiskFile/DiskFolder with WindowsDiskFile/WindowsDiskFolder

Because both set of classes derive from AbstractFile/AbstractFolder, they can be used together so that WindowsDiskFile/WindowsDiskFolder are only used in specific cases where access to a long file or folder is needed.

// Select a file with a normal file name
AbstractFile file = new DiskFile( @"D:\Data\SomeFile.dat" );

// Select a folder with a long path
AbstractFolder destinationFolder = new WindowsDiskFolder( @"D:\SomeFolder\" + veryLongPath );

// Copy the file to the destination folder
file.CopyTo( destinationFolder, true );

' Select a file with a normal file name
Dim file As AbstractFile = New DiskFile("D:\Data\SomeFile.dat")

' Select a folder with a long path
Dim destinationFolder As AbstractFolder = New WindowsDiskFolder("D:\SomeFolder\" & veryLongPath)

' Copy the file to the destination folder
file.CopyTo(destinationFolder, True)

Unzipping into a WindowsDiskFolder

A classic problem situation is dealing with zip archives. Zip archives can contain items with long names. Unzipping such an item into a DiskFolder would make the .NET framework throw a %System.IO.PathTooLongException%. By unzipping into a WindowsDiskFolder, items with long names will be unzipped into WindowsDiskFile objects that can handle the name.

// Select a zip file
AbstractFile zipFile = new DiskFile( @"D:\Data\SomeZipFile.zip" );

// If the zip file exists
if( zipFile.Exists )
  // Delete it
  zipFile.Delete();

// Create a logical zip archive around the zip file
ZipArchive zip = new ZipArchive( zipFile );

// Select an existing file as a source
AbstractFile file = new DiskFile( @"D:\Data\SomeFile.dat" );

// Select a specific long name in the zip archive
AbstractFile zippedFile = zip.GetFile( veryLongFileName );

// Copy the source file to the long named zipped file
file.CopyTo( zippedFile, true );

// Select a WindowsDiskFolder as the destination folder
AbstractFolder destinationFolder = new WindowsDiskFolder( @"D:\SomeFolder" );
      
// Unzip the files in the zip archive to the destination folder
zip.CopyFilesTo( destinationFolder, true, true );

' Select a zip file
Dim zipFile As AbstractFile = New DiskFile("D:\Data\SomeZipFile.zip")

' If the zip file exists
If zipFile.Exists Then
  ' Delete it
  zipFile.Delete()
End If

' Create a logical zip archive around the zip file
Dim zip As New ZipArchive(zipFile)

' Select an existing file as a source
Dim file As AbstractFile = New DiskFile("D:\Data\SomeFile.dat")

' Select a specific long name in the zip archive
Dim zippedFile As AbstractFile = zip.GetFile(veryLongFileName)

' Copy the source file to the long named zipped file
file.CopyTo(zippedFile, True)

' Select a WindowsDiskFolder as the destination folder
Dim destinationFolder As AbstractFolder = New WindowsDiskFolder("D:\SomeFolder")

' Unzip the files in the zip archive to the destination folder
zip.CopyFilesTo(destinationFolder, True, True)

Zipping from WindowsDiskFile and WindowsDiskFolder

Another classic problem is zipping from a disk that contains files with long names or a folder structure that amounts to a long path. Using DiskFolder, an exception is thrown when an item that cannot be handled is encountered. Using WindowsDiskFile and WindowsDiskFolder objects as sources, the files can be handled properly.

// Select a zip file
AbstractFile zipFile = new DiskFile( @"D:\Data\SomeZipFile.zip" );

// If the zip file exists
if( zipFile.Exists )
  // Delete it
  zipFile.Delete();

// Create a logical zip archive around the zip file
ZipArchive zip = new ZipArchive( zipFile );

using( AutoBatchUpdate batch = new AutoBatchUpdate( zip ) )
{
  // Select an existing WindowsDiskFile with a long file name
  AbstractFile file = new WindowsDiskFile( @"D:\Data\" + veryLongFileName );

  // Add it to the zip archive
  file.CopyTo( zip, true );

  // Select a folder that might contain files with long names or a sub folder structure that amounts to a long path
  AbstractFolder folder = new WindowsDiskFolder( @"D:\OtherFolderThatContainsFileWithLongNames" );
  
  // Add the folder to the zip archive
  folder.CopyFilesTo( zip, true, true );
}

' Select a zip file
Dim zipFile As AbstractFile = New DiskFile("D:\Data\SomeZipFile.zip")

' If the zip file exists
If zipFile.Exists Then
  ' Delete it
  zipFile.Delete()
End If

' Create a logical zip archive around the zip file
Dim zip As New ZipArchive(zipFile)

Using batch As New AutoBatchUpdate(zip)
  ' Select an existing WindowsDiskFile with a long file name
  Dim file As AbstractFile = New WindowsDiskFile("D:\Data\" & veryLongFileName)

  ' Add it to the zip archive
  file.CopyTo(zip, True)

  ' Select a folder that might contain files with long names or a sub folder structure that amounts to a long path
  Dim folder As AbstractFolder = New WindowsDiskFolder("D:\OtherFolderThatContainsFileWithLongNames")

  ' Add the folder to the zip archive
  folder.CopyFilesTo(zip, True, True)
End Using

If you have existing code which use DiskFile and DiskFolder that you do not wish to modify but would like to benefit from long path support, you can instruct DiskFile and DiskFolder to automatically use WindowsDiskFile and WindowsDiskFolder internally. This way, they will support long paths the same way.

// Create an instance of the Windows IO Handler
Xceed.FileSystem.IO.IIOHandler ioHandler = new Win32IOHandler();

// Instruct DiskFile and DiskFolder to use our IO handler from now on
DiskFile.DefaultIOHandler = ioHandler;

// Select a DiskFile with a long file name
AbstractFile file = new DiskFile( @"D:\" + veryLongFileName );

// Select a DiskFolder with a long path
AbstractFolder folder = new DiskFolder( @"D:\" + veryLongPath );

' Create an instance of the Windows IO Handler
Dim ioHandler As Xceed.FileSystem.IO.IIOHandler = New Win32IOHandler()

' Instruct DiskFile and DiskFolder to use our IO handler from now on
DiskFile.DefaultIOHandler = ioHandler

' Select a DiskFile with a long file name
Dim file As AbstractFile = New DiskFile("D:\" & veryLongFileName)

' Select a DiskFolder with a long path
Dim folder As AbstractFolder = New DiskFolder("D:\" & veryLongPath)