Working with 7z Archives

Overview

7-Zip is a file archiver with a high compression ratio. Aspose.ZIP API lets work with creating and managing 7-Zip archives in your applications without the need of any other 3rd party applications. Aspose.ZIP API provides  SevenZipArchive class to work with 7-Zip archives. This class provides various methods to perform operations on archives. API provides the  SevenZipArchiveEntry class to represents a single file within the 7z archive.

Create a 7-Zip Single Entry

The following code example demonstrates how to create a 7-Zip entry using SevenZipArchive instance.

    using (FileStream sevenZipFile = File.Open("archive.7z", FileMode.Create))
    {
        using (var archive = new SevenZipArchive())
        {
            archive.CreateEntry("data.bin", "file.dat");
            archive.Save(sevenZipFile);
        }
    }

Create 7-Zip Archive Entries

The SevenZipArchive class provides CreateEntries methods to add files and directories recursively in the given directory given. The following code example demonstrates how to create 7-Zip archive entries.

    using (SevenZipArchive archive = new SevenZipArchive())
    {
        archive.CreateEntries(dataDir);
        archive.Save("SevenZip.7z");
    }

7-Zip Encryption Settings

Aspose.ZIP API provides SevenZipAESEncryptionSettings class which provides Settings for AES encryption or decryption for 7z archives. The following code example demonstrates how to provide AES Encryption Settings.

    using (var archive = new SevenZipArchive(new SevenZipEntrySettings(null, new SevenZipAESEncryptionSettings("p@s$"))))
    {
        archive.CreateEntry("data.bin", new MemoryStream(new byte[] { 0x00, 0xFF }));
        archive.Save("archive.7z");
    }

The AES-256 is the only possible encryption method for the 7z archive.

7-Zip Archive with LZMA Compression

The following code example demonstrates how to create a 7z archive with LZMA compression and AES encryption.

Steps: Create a 7z Archive with LZMA Compression and AES Encryption via C#

1. Open a file stream for the output 7z archive using FileMode.Create.
2. Create an instance of the SevenZipArchive class.
3. Use the CreateEntry method to add an entry to the archive, specifying:
   • The file to be compressed.
   • LZMA compression settings using SevenZipLZMACompressionSettings.
   • AES encryption settings using SevenZipAESEncryptionSettings (with a password).
4. Save the archive using the Save method to write the compressed and encrypted data to the file.

    using (FileStream sevenZipFile = File.Open("archive.7z", FileMode.Create))
    {
        using (var archive = new SevenZipArchive())
        {
            archive.CreateEntry("entry1.bin", 
                new MemoryStream(new byte[] { 0x00, 0xFF }), 
                new SevenZipEntrySettings(new SevenZipLZMACompressionSettings(), 
                new SevenZipAESEncryptionSettings("test1")), 
                new FileInfo("data1.bin"));
            archive.Save(sevenZipFile);
        }
    }

Similarly you can compose 7z archive with BZip2, PPMd and LZMA2 compression method, or store files without compression.

Solid 7-Zip Archive Composition

Solid compressed archives benefit greatly from the data with high redundancy. It treats all entries as a sinlge data stream. The following code example demonstrates how to create a solid archive from a directory with LZMA2 compression.

    using (var archive = new SevenZipArchive(new SevenZipEntrySettings(new SevenZipLZMA2CompressionSettings()){ Solid = true }))
    {
        archive.CreateEntries(dataDir);
        archive.Save("Solid.7z");
    }

Setting Different Password for Entries

The following code example demonstrates how to create an archive with entries encrypted with different passwords for each entry.

Steps: Create a 7z Archive with LZMA Compression and AES Encryption via C#

1. Open a file stream to create the 7z archive using FileMode.Create.
2. Prepare the files (FileInfo objects) that you want to add as entries to the archive.
3. Create an instance of the SevenZipArchive class.
4. For each entry, use the CreateEntry method to add the file to the archive:
   • Specify the compression method (in this case, SevenZipStoreCompressionSettings).
   • Set a different password for each entry using SevenZipAESEncryptionSettings.
5. Save the archive using the Save method to write the encrypted entries to the file.

    using (FileStream sevenZipFile = File.Open("archive.7z", FileMode.Create))
    {
        FileInfo fi1 = new FileInfo("data1.bin");
        FileInfo fi2 = new FileInfo("data2.bin");
        FileInfo fi3 = new FileInfo("data3.bin");
        using (var archive = new SevenZipArchive())
        {
            archive.CreateEntry("entry1.bin", fi1, false, new SevenZipEntrySettings(new SevenZipStoreCompressionSettings(), new SevenZipAESEncryptionSettings("test1")));
            archive.CreateEntry("entry2.bin", fi2, false, new SevenZipEntrySettings(new SevenZipStoreCompressionSettings(), new SevenZipAESEncryptionSettings("test2")));
            archive.CreateEntry("entry3.bin", fi3, false, new SevenZipEntrySettings(new SevenZipStoreCompressionSettings(), new SevenZipAESEncryptionSettings("test3")));
            archive.Save(sevenZipFile);
        }
    }

Extraction of 7z archives

Now Aspose.ZIP can extract LZMA, LZMA2, BZip2 and PPMd compressed archives.

The following code example demonstrates how to extract 7z archive to directory.

    using (SevenZipArchive archive = new SevenZipArchive("archive.7z"))
    {
        archive.ExtractToDirectory("ExtractionFolder");
    }