How can I merge 2 zip files into 1?

Question

i have 2 zip files (zip1 and zip2), i need merge this files in one, how can i solve it? I understand that I can fix it decompressing ZIP1 to a temp folder and then add it to zip2, but i think it is inefficient, what is the faster method?

I'm using System.IO.Compression library...

I use this code to explore Zip2:

 using (ZipArchive archive = ZipFile.OpenRead(Zip2))
 {
    foreach (ZipArchiveEntry entry in archive.Entries)
    {
       /*...*/
    }
 }

PD/: The Zip1 and Zip2 files have FILES, FOLDERS AND SUBFOLDERS

Answer 1

I haven't really tested this, but you can give it a try:

    public ZipArchive Merge(List<ZipArchive> archives)
    {
        if (archives == null) throw new ArgumentNullException("archives");
        if (archives.Count == 1) return archives.Single();

        using (var memoryStream = new MemoryStream())
        {
            using (var archive = new ZipArchive(memoryStream, ZipArchiveMode.Create, true))
            {
                foreach (var zipArchive in archives)
                {
                    foreach (var zipArchiveEntry in zipArchive.Entries)
                    {
                        var file = archive.CreateEntry(zipArchiveEntry.FullName);

                        using (var entryStream = file.Open()) {
                            using (var streamWriter = new StreamWriter(entryStream)) { streamWriter.Write(zipArchiveEntry.Open()); }
                        }
                    }
                }

                return archive;
            }
        }
    }

Answer 2

I had an equivalent problem. The zip files came from another process as byte arrays. This method adds their contents to an existing ZipArchive.

using System.IO;
using System.IO.Compression;

        /// <summary>
        /// Copies the contents of a zip "file" represented as a byte array
        /// to the given ZipArchive.
        /// </summary>
        /// <param name="targetArchive">The archive to which to add the entries.</param>
        /// <param name="zippedSourceBuffer">The source data as zip "file" in a byte array.</param>
        public static void addZipBufferToZipArchive(ZipArchive targetArchive, byte[] zippedSourceBuffer)
        {
            using (MemoryStream zippedSourceStream = new MemoryStream(zippedSourceBuffer))
            {
                using (ZipArchive sourceArchive = new ZipArchive(zippedSourceStream))
                {
                    foreach (ZipArchiveEntry sourceEntry in sourceArchive.Entries)
                    {
                        ZipArchiveEntry targetEntry = targetArchive.CreateEntry(sourceEntry.FullName);
                        using (Stream targetEntryStream = targetEntry.Open())
                        {
                            using (Stream sourceStream = sourceEntry.Open())
                            {
                                sourceStream.CopyTo(targetEntryStream);
                            }
                        }
                    }
                }
            }
        }

There does not appear to be any way to directly move a ZipArchiveEntry from one ZipArchive to another, so I resorted to unpacking the source and repacking it to the target via the copy operation.

If you already have a ZipArchive as source, you wouldn't need the MemoryStream zippedSourceStream and could modify the code to use sourceArchive directly as the method parameter.