/// <summary>
        /// Отправка файла клиенту
        /// </summary>
        /// <param name="id">Идентификатор файла</param>
        /// <returns></returns>
        public async Task<IActionResult> GetFile(Guid id)
        {
            var fileList = new List<( byte[] filebytes, string filename)>();
            try
            {
                using (SqlConnection con = new SqlConnection(dbConString))
                {
                    if (con.State != ConnectionState.Open)
                        await con.OpenAsync();                 
                        try
                        {
                            using (SqlCommand cmd = new SqlCommand("GetFile", con))
                            {
                              cmd.CommandType = CommandType.StoredProcedure;

                             SqlParameter masterId = cmd.Parameters.Add("@id", SqlDbType.UniqueIdentifier);
                             masterId.Value = id;
 
                            using (SqlDataReader reader =await cmd.ExecuteReaderAsync())
                            {
                                if (reader.HasRows)
                                {
                                    while (await reader.ReadAsync())
                                    {
                                        fileList.Add(((byte[])reader["File"], (string)reader["FileName"]));                               
                                    }
                                }
                                else
                                {
                                    throw new Exception();
                                }
                            }
                            }
                        }
                        catch (Exception ex)
                        {
                            return Json(new { success = false });
                        }                 
                }

            }
            catch (Exception)
            {
                throw;
            }

            if (fileList.Count>1)
            {
                //несколько файлов-упаковываем в архив

                using (var compressedFileStream = new MemoryStream())
                // using (FileStream compressedFileStream = new FileStream(@"C:\Users\antonov\Desktop\1\release.zip", FileMode.CreateNew))
                // через FileStream  файл сохраняется корректно


                //Create an archive and store the stream in memory.
                using (var zipArchive = new ZipArchive(compressedFileStream, ZipArchiveMode.Create, true))
                {
                    foreach (var (filebytes, filename) in fileList)
                    {
                        //Create a zip entry for each attachment
                        var zipEntry = zipArchive.CreateEntry(filename);

                        //Get the stream of the attachment
                        using (var originalFileStream = new MemoryStream(filebytes))
                        using (var zipEntryStream = zipEntry.Open())
                        {
                            //Copy the attachment stream to the zip entry stream
                            await originalFileStream.CopyToAsync(zipEntryStream);
                        }
                    }
                    return new FileContentResult(compressedFileStream.ToArray(), "application/zip") { FileDownloadName = "Files.zip" };
                    //пробовал  менять "application/zip" на "application/octet-stream"- не помогает
                }
            }
            else
            {
                var fl = fileList.FirstOrDefault();
                return File(fl.filebytes, "application/octet-stream", fl.filename);
            }
        }

document.getElementById("GetFileButton").addEventListener('click', function (event) {
    let varid = $("#InputGuid").val();
    window.location = '/Uploader/GetFile?id=' + varid;
});

  using (var zipArchive = new ZipArchive(compressedFileStream, ZipArchiveMode.Create, false))

       using (var compressedFileStream = new MemoryStream())
                {
                    using (var zipArchive = new ZipArchive(compressedFileStream, ZipArchiveMode.Create, true))
                    {                  
                        foreach (var (filebytes, filename) in fileList)
                        {
                            //Create a zip entry for each attachment
                            var zipEntry = zipArchive.CreateEntry(filename);

                            //Get the stream of the attachment
                            using (var originalFileStream = new MemoryStream(filebytes))
                            using (var zipEntryStream = zipEntry.Open())
                            {
                                //Copy the attachment stream to the zip entry stream
                                await originalFileStream.CopyToAsync(zipEntryStream);
                            }
                        }                      
                    }
                    return new FileContentResult(compressedFileStream.ToArray(), "application/zip") { FileDownloadName = "Files.zip" };
                }