How to Avoid Empty Entries When Creating an In-Memory ZIP Archive with MemoryStream?

Creating a ZIP Archive in Memory with MemoryStream: Overcoming the Empty Entry Issue

When attempting to create a ZIP archive in memory using a MemoryStream, developers have encountered a peculiar problem: the created archive contains an empty file even though the corresponding text file is written. This behavior is attributed to a missing step in the process.

To resolve this issue, the key is to call Dispose on the ZipArchive object before attempting to access its underlying stream. This practice is necessary because ZipArchive writes final bytes to the archive's checksum, rendering it complete. However, if we want the stream to remain open for further use, we need to pass true as the third parameter to ZipArchive.

Here's a revised code snippet that incorporates this solution:

using (var memoryStream = new MemoryStream())
{
    using (var archive = new ZipArchive(memoryStream, ZipArchiveMode.Create, true))
    {
        var demoFile = archive.CreateEntry("foo.txt");

        using (var entryStream = demoFile.Open())
        using (var streamWriter = new StreamWriter(entryStream))
        {
            streamWriter.Write("Bar!");
        }
    }

    using (var fileStream = new FileStream(@"C:\Temp\test.zip", FileMode.Create))
    {
        memoryStream.Seek(0, SeekOrigin.Begin);
        memoryStream.CopyTo(fileStream);
    }
}

By following this approach, developers can successfully create a complete ZIP archive in memory using a MemoryStream, without encountering the problem of empty entries.

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