I am copying files from one zip file to another in certain circumstances. I am wondering if there is a better way to do it than what I came up with:

using FileStream sourceFileStream = new FileStream(source.FileName, FileMode.Open);
using FileStream targetFileStream = new FileStream(target.FileName, FileMode.Open, FileAccess.ReadWrite);
using ZipArchive sourceZip = new ZipArchive(sourceFileStream, ZipArchiveMode.Read);
using ZipArchive targetZip = new ZipArchive(targetFileStream, ZipArchiveMode.Update);
ZipArchiveEntry sourceEntry = sourceZip.GetEntry(filePathInArchive);
if (sourceEntry == null) 
    return;
ZipArchiveEntry targetEntry = targetZip.GetEntry(filePathInArchive);
if (targetEntry != null) 
    targetEntry.Delete();
targetZip.CreateEntry(filePathInArchive);
targetEntry = targetZip.GetEntry(filePathInArchive);
if (targetEntry != null)
{
    Stream writer = targetEntry.Open();
    Stream reader = sourceEntry.Open();

    int b;
    do
    {
        b = reader.ReadByte();
        writer.WriteByte((byte)b);
    } while (b != -1);


    writer.Close();
    reader.Close();
}

Tips and suggestions would be appreciated.

CodePudding user response：

You can iterate each entry from source archive with opening its streams and using Stream.CopyTo write source entry content to target entry.

From C# 8.0 it looks compact and works fine:

static void CopyZipEntries(string sourceZipFile, string targetZipFile)
{
    using FileStream sourceFS = new FileStream(sourceZipFile, FileMode.Open);
    using FileStream targetFS = new FileStream(targetZipFile, FileMode.Open);

    using ZipArchive sourceZIP = new ZipArchive(sourceFS, ZipArchiveMode.Read, false, Encoding.GetEncoding(1251));
    using ZipArchive targetZIP = new ZipArchive(targetFS, ZipArchiveMode.Update, false, Encoding.GetEncoding(1251));

    foreach (ZipArchiveEntry sourceEntry in sourceZIP.Entries)
    {
        // 'is' is replacement for 'null' check
        if (targetZIP.GetEntry(sourceEntry.FullName) is ZipArchiveEntry existingTargetEntry)
            existingTargetEntry.Delete();

        using (Stream targetEntryStream = targetZIP.CreateEntry(sourceEntry.FullName).Open())
        {
            sourceEntry.Open().CopyTo(targetEntryStream);
        }
    }
}

With earlier than C# 8.0 versions it works fine too, but more braces needed:

static void CopyZipEntries(string sourceZipFile, string targetZipFile)
{
    using (FileStream sourceFS = new FileStream(sourceZipFile, FileMode.Open))
    {
        using (FileStream targetFS = new FileStream(targetZipFile, FileMode.Open))
        {
            using (ZipArchive sourceZIP = new ZipArchive(sourceFS, ZipArchiveMode.Read, false, Encoding.GetEncoding(1251)))
            {
                using (ZipArchive targetZIP = new ZipArchive(targetFS, ZipArchiveMode.Update, false, Encoding.GetEncoding(1251)))
                {
                    foreach (ZipArchiveEntry sourceEntry in sourceZIP.Entries)
                    {
                        if (targetZIP.GetEntry(sourceEntry.FullName) is ZipArchiveEntry existingTargetEntry)
                        {
                            existingTargetEntry.Delete();
                        }

                        using (Stream target = targetZIP.CreateEntry(sourceEntry.FullName).Open())
                        {
                            sourceEntry.Open().CopyTo(target);
                        }
                    }
                }
            }
        }
    }
}

For single specified file copy just replace bottom part from foreach loop to if condition:

static void CopyZipEntry(string fileName, string sourceZipFile, string targetZipFile)
{
    // ...

    // It means specified file exists in source ZIP-archive
    // and we can copy it to target ZIP-archive
    if (sourceZIP.GetEntry(fileName) is ZipArchiveEntry sourceEntry) 
    {
        if (targetZIP.GetEntry(sourceEntry.FullName) is ZipArchiveEntry existingTargetEntry)
            existingTargetEntry.Delete();

        using (Stream targetEntryStream = targetZIP.CreateEntry(sourceEntry.FullName).Open())
        {
            sourceEntry.Open().CopyTo(targetEntryStream);
        }
    }
    else
        MessageBox.Show("Source ZIP-archive doesn't contains file "   fileName);
}