How to: Compress and extract files
The System.IO.Compression namespace contains the following classes for compressing and decompressing files and streams. You also can use these types to read and modify the contents of a compressed file:
The following examples show some of the operations you can perform with compressed files. These examples require the following NuGet packages to be added to your project:
If you're using .NET Framework, add references to these two libraries to your project:
System.IO.CompressionSystem.IO.Compression.FileSystem
Example 1: Create and extract a .zip file
The following example shows how to create and extract a compressed .zip file by using the ZipFile class. The example compresses the contents of a folder into a new .zip file, and then extracts the file to a new folder.
To run the sample, create a start folder in your program folder and populate it with files to zip.
using System;
using System.IO.Compression;
class Program
{
static void Main(string[] args)
{
string startPath = @".\start";
string zipPath = @".\result.zip";
string extractPath = @".\extract";
ZipFile.CreateFromDirectory(startPath, zipPath);
ZipFile.ExtractToDirectory(zipPath, extractPath);
}
}
Imports System.IO.Compression
Module Module1
Sub Main()
Dim startPath As String = ".\start"
Dim zipPath As String = ".\result.zip"
Dim extractPath As String = ".\extract"
ZipFile.CreateFromDirectory(startPath, zipPath)
ZipFile.ExtractToDirectory(zipPath, extractPath)
End Sub
End Module
Example 2: Extract specific file extensions
The following example iterates through the contents of an existing .zip file and extracts files with a .txt extension. It uses the ZipArchive class to access the .zip file, and the ZipArchiveEntry class to inspect the individual entries. The extension method ExtractToFile for the ZipArchiveEntry object is available in the System.IO.Compression.ZipFileExtensions class.
To run the sample, place a .zip file called result.zip in your program folder. When prompted, provide a folder name to extract to.
Important
When unzipping files, you must look for malicious file paths, which can escape from the directory you unzip into. This is known as a path traversal attack. The following example demonstrates how to check for malicious file paths and provides a safe way to unzip.
using System;
using System.IO;
using System.IO.Compression;
class Program
{
static void Main(string[] args)
{
string zipPath = @".\result.zip";
Console.WriteLine("Provide path where to extract the zip file:");
string extractPath = Console.ReadLine();
// Normalizes the path.
extractPath = Path.GetFullPath(extractPath);
// Ensures that the last character on the extraction path
// is the directory separator char.
// Without this, a malicious zip file could try to traverse outside of the expected
// extraction path.
if (!extractPath.EndsWith(Path.DirectorySeparatorChar.ToString(), StringComparison.Ordinal))
extractPath += Path.DirectorySeparatorChar;
using (ZipArchive archive = ZipFile.OpenRead(zipPath))
{
foreach (ZipArchiveEntry entry in archive.Entries)
{
if (entry.FullName.EndsWith(".txt", StringComparison.OrdinalIgnoreCase))
{
// Gets the full path to ensure that relative segments are removed.
string destinationPath = Path.GetFullPath(Path.Combine(extractPath, entry.FullName));
// Ordinal match is safest, case-sensitive volumes can be mounted within volumes that
// are case-insensitive.
if (destinationPath.StartsWith(extractPath, StringComparison.Ordinal))
entry.ExtractToFile(destinationPath);
}
}
}
}
}
Imports System.IO
Imports System.IO.Compression
Module Module1
Sub Main()
Dim zipPath As String = ".\result.zip"
Console.WriteLine("Provide path where to extract the zip file:")
Dim extractPath As String = Console.ReadLine()
' Normalizes the path.
extractPath = Path.GetFullPath(extractPath)
' Ensures that the last character on the extraction path
' is the directory separator char.
' Without this, a malicious zip file could try to traverse outside of the expected
' extraction path.
If Not extractPath.EndsWith(Path.DirectorySeparatorChar.ToString(), StringComparison.Ordinal) Then
extractPath += Path.DirectorySeparatorChar
End If
Using archive As ZipArchive = ZipFile.OpenRead(zipPath)
For Each entry As ZipArchiveEntry In archive.Entries
If entry.FullName.EndsWith(".txt", StringComparison.OrdinalIgnoreCase) Then
' Gets the full path to ensure that relative segments are removed.
Dim destinationPath As String = Path.GetFullPath(Path.Combine(extractPath, entry.FullName))
' Ordinal match is safest, case-sensitive volumes can be mounted within volumes that
' are case-insensitive.
If destinationPath.StartsWith(extractPath, StringComparison.Ordinal) Then
entry.ExtractToFile(destinationPath)
End If
End If
Next
End Using
End Sub
End Module
Example 3: Add a file to an existing .zip file
The following example uses the ZipArchive class to access an existing .zip file, and adds a file to it. The new file gets compressed when you add it to the existing .zip file.
using System;
using System.IO;
using System.IO.Compression;
namespace ConsoleApplication
{
class Program
{
static void Main(string[] args)
{
using (FileStream zipToOpen = new FileStream(@"c:\users\exampleuser\release.zip", FileMode.Open))
{
using (ZipArchive archive = new ZipArchive(zipToOpen, ZipArchiveMode.Update))
{
ZipArchiveEntry readmeEntry = archive.CreateEntry("Readme.txt");
using (StreamWriter writer = new StreamWriter(readmeEntry.Open()))
{
writer.WriteLine("Information about this package.");
writer.WriteLine("========================");
}
}
}
}
}
}
Imports System.IO
Imports System.IO.Compression
Module Module1
Sub Main()
Using zipToOpen As FileStream = New FileStream("c:\users\exampleuser\release.zip", FileMode.Open)
Using archive As ZipArchive = New ZipArchive(zipToOpen, ZipArchiveMode.Update)
Dim readmeEntry As ZipArchiveEntry = archive.CreateEntry("Readme.txt")
Using writer As StreamWriter = New StreamWriter(readmeEntry.Open())
writer.WriteLine("Information about this package.")
writer.WriteLine("========================")
End Using
End Using
End Using
End Sub
End Module
Example 4: Compress and decompress .gz files
You can also use the GZipStream and DeflateStream classes to compress and decompress data. They use the same compression algorithm. You can decompress GZipStream objects that are written to a .gz file by using many common tools. The following example shows how to compress and decompress a directory of files by using the GZipStream class:
using System;
using System.IO;
using System.IO.Compression;
public class Program
{
private static string directoryPath = @".\temp";
public static void Main()
{
DirectoryInfo directorySelected = new DirectoryInfo(directoryPath);
Compress(directorySelected);
foreach (FileInfo fileToDecompress in directorySelected.GetFiles("*.gz"))
{
Decompress(fileToDecompress);
}
}
public static void Compress(DirectoryInfo directorySelected)
{
foreach (FileInfo fileToCompress in directorySelected.GetFiles())
{
using (FileStream originalFileStream = fileToCompress.OpenRead())
{
if ((File.GetAttributes(fileToCompress.FullName) &
FileAttributes.Hidden) != FileAttributes.Hidden & fileToCompress.Extension != ".gz")
{
using (FileStream compressedFileStream = File.Create(fileToCompress.FullName + ".gz"))
{
using (GZipStream compressionStream = new GZipStream(compressedFileStream,
CompressionMode.Compress))
{
originalFileStream.CopyTo(compressionStream);
}
}
FileInfo info = new FileInfo(directoryPath + Path.DirectorySeparatorChar + fileToCompress.Name + ".gz");
Console.WriteLine($"Compressed {fileToCompress.Name} from {fileToCompress.Length.ToString()} to {info.Length.ToString()} bytes.");
}
}
}
}
public static void Decompress(FileInfo fileToDecompress)
{
using (FileStream originalFileStream = fileToDecompress.OpenRead())
{
string currentFileName = fileToDecompress.FullName;
string newFileName = currentFileName.Remove(currentFileName.Length - fileToDecompress.Extension.Length);
using (FileStream decompressedFileStream = File.Create(newFileName))
{
using (GZipStream decompressionStream = new GZipStream(originalFileStream, CompressionMode.Decompress))
{
decompressionStream.CopyTo(decompressedFileStream);
Console.WriteLine($"Decompressed: {fileToDecompress.Name}");
}
}
}
}
}
Imports System.IO
Imports System.IO.Compression
Module Module1
Private directoryPath As String = ".\temp"
Public Sub Main()
Dim directorySelected As New DirectoryInfo(directoryPath)
Compress(directorySelected)
For Each fileToDecompress As FileInfo In directorySelected.GetFiles("*.gz")
Decompress(fileToDecompress)
Next
End Sub
Public Sub Compress(directorySelected As DirectoryInfo)
For Each fileToCompress As FileInfo In directorySelected.GetFiles()
Using originalFileStream As FileStream = fileToCompress.OpenRead()
If (File.GetAttributes(fileToCompress.FullName) And FileAttributes.Hidden) <> FileAttributes.Hidden And fileToCompress.Extension <> ".gz" Then
Using compressedFileStream As FileStream = File.Create(fileToCompress.FullName & ".gz")
Using compressionStream As New GZipStream(compressedFileStream, CompressionMode.Compress)
originalFileStream.CopyTo(compressionStream)
End Using
End Using
Dim info As New FileInfo(directoryPath & Path.DirectorySeparatorChar & fileToCompress.Name & ".gz")
Console.WriteLine($"Compressed {fileToCompress.Name} from {fileToCompress.Length.ToString()} to {info.Length.ToString()} bytes.")
End If
End Using
Next
End Sub
Private Sub Decompress(ByVal fileToDecompress As FileInfo)
Using originalFileStream As FileStream = fileToDecompress.OpenRead()
Dim currentFileName As String = fileToDecompress.FullName
Dim newFileName = currentFileName.Remove(currentFileName.Length - fileToDecompress.Extension.Length)
Using decompressedFileStream As FileStream = File.Create(newFileName)
Using decompressionStream As GZipStream = New GZipStream(originalFileStream, CompressionMode.Decompress)
decompressionStream.CopyTo(decompressedFileStream)
Console.WriteLine($"Decompressed: {fileToDecompress.Name}")
End Using
End Using
End Using
End Sub
End Module
