Procedura: Comprimere ed estrarre file
Lo spazio dei nomi System.IO.Compression contiene le seguenti classi per la compressione e la decompressione di file e flussi. È possibile usare queste classi anche per leggere e modificare il contenuto di un file compresso:
Gli esempi seguenti mostrano alcune delle operazioni che è possibile eseguire con i file compressi. Questi esempi richiedono l'aggiunta al progetto dei seguenti pacchetti NuGet:
Se si usa .NET Framework, aggiungere riferimenti a queste due librerie al progetto:
System.IO.CompressionSystem.IO.Compression.FileSystem
Esempio 1: creare ed estrarre un file con estensione zip
Nell'esempio seguente viene illustrato come creare ed estrarre un file ZIP compresso usando la classe ZipFile. L'esempio comprime il contenuto di una cartella in un nuovo file ZIP e quindi estrae il file in una nuova cartella.
Per eseguire l'esempio, creare una cartella start nella cartella del programma e copiarvi i file da comprimere.
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
Esempio 2: estrarre estensioni file specifiche
Il seguente esempio mostra come eseguire l'iterazione del contenuto di un file ZIP esistente ed estrarre i file con estensione .txt. Usa la classe ZipArchive per accedere al file ZIP e la classe ZipArchiveEntry per controllare le singole voci. Il metodo di estensione ExtractToFile per l'oggetto ZipArchiveEntry è disponibile nella classe System.IO.Compression.ZipFileExtensions.
Per eseguire l'esempio, inserire un file ZIP denominato result.zip nella cartella del programma. Quando richiesto, specificare un nome di cartella in cui estrarre i file.
Importante
Quando si decomprimono i file, è necessario cercare percorsi dannosi che possono sfuggire dalla directory in cui si esegue la decompressione. Si tratta di un attacco noto come attacco path traversal. L'esempio seguente illustra come verificare la presenza di percorsi file dannosi e offre un metodo sicuro per la decompressione.
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
Esempio 3: aggiungere un nuovo file in un file ZIP esistente
L'esempio seguente usa la classe ZipArchive per accedere a un file ZIP esistente e aggiunge un nuovo file al file compresso. Il nuovo file viene compresso quando lo si aggiunge al file ZIP esistente.
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
Esempio 4: comprimere e decomprimere file con estensione .gz
È possibile usare anche le classi GZipStream e DeflateStream per comprimere e decomprimere dati. Queste due classi usano lo stesso algoritmo di compressione. È possibile decomprimere gli oggetti GZipStream scritti in un file con estensione gz con molti strumenti comuni. L'esempio seguente illustra come comprimere e decomprimere una directory di file usando la classe GZipStream:
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
