Create a Flat ZIP Archive in C# .NET

readme.md

Learn how to create flat ZIP archives in C# .NET: https://blog.aspose.com/2022/01/17/create-a-flat-zip-archive-in-csharp/

create-flat-zip.cs

// Load ZIP archive
using (Archive outer = new Archive("Archives/nested-archive.zip"))
{
    // Create a list to delete inner ZIP entries after extraction
    List<ArchiveEntry> entriesToDelete = new List<ArchiveEntry>();

    // Create a list to add names of files in inner ZIP archives
    List<string> namesToInsert = new List<string>();

    // Create a list to add stream objects of files in inner ZIP archives
    List<MemoryStream> contentToInsert = new List<MemoryStream>();

    // Loop through entries in the parent ZIP
    foreach (ArchiveEntry entry in outer.Entries)
    {
        // Check if entry is a ZIP file
        if (entry.Name.EndsWith(".zip", StringComparison.InvariantCultureIgnoreCase)) 
        {
            // Add entry to list to keep reference in order to remove it from the archive later
            entriesToDelete.Add(entry); 

            // Create stream object to open the ZIP archive
            MemoryStream innerCompressed = new MemoryStream();
            entry.Open().CopyTo(innerCompressed);

            // Load the ZIP archive from stream object 
            using (Archive inner = new Archive(innerCompressed))
            {
                // Loop over entries of archive
                foreach (ArchiveEntry ie in inner.Entries) 
                {
                    // Keep the name of entry in list
                    namesToInsert.Add(ie.Name); 

                    // Extract archive entry into a stream object
                    MemoryStream content = new MemoryStream();
                    ie.Open().CopyTo(content);

                    // Add entry to the list
                    contentToInsert.Add(content);
                }
            }
        }
    }

    // Delete the inner ZIP archives
    foreach (ArchiveEntry e in entriesToDelete)
        outer.DeleteEntry(e);

    // Insert the files of inner ZIP archives to parent ZIP archive
    for (int i = 0; i < namesToInsert.Count; i++)
        outer.CreateEntry(namesToInsert[i], contentToInsert[i]);

    outer.Save("Archives/flatten.zip");
}