DBのBlob列に格納されたバイナリファイルをzipに圧縮してダウンロードする

    [HttpGet("{id}/zip")]
    [ProducesResponseType(StatusCodes.Status200OK)]
    [ProducesResponseType(StatusCodes.Status404NotFound)]
    public async Task<IActionResult> GetZipById(int id)
    {
        Blob record = // DbContextからBlobを取得
        if (record == null) return NotFound();
        using var memoryStream = new MemoryStream();

        using (var archive = new ZipArchive(memoryStream, ZipArchiveMode.Create, true))
        {
            var entry = archive.CreateEntry($"file{record.Extension}", CompressionLevel.Optimal);
            using (var es = entry.Open())
            {
                es.Write(record.Bytes!, 0, record.Bytes!.Length);
            }
        }
        return File(memoryStream.ToArray(), "application/zip", $"file.zip");
    }

public record Blob 
{
    public int Id { get; set; }

    public byte[]? Bytes { get; set; } = Array.Empty<byte>();

    public string Contextype { get; set; } = string.Empty;

    public string Extension { get; set; } = string.Empty;
}