i m getting error on CopyToAsync when filelist is having more than 1 file in case of 1 file it is working fine. issue could be related to concurrency i am not sure about that solution will be really appreciated

        CloudStorageAccount cloudStorageAccount = CloudStorageAccount.Parse(_configuration["AzureBlobStorage"]);
        CloudBlobClient cloudBlobClient = cloudStorageAccount.CreateCloudBlobClient();
        CloudBlobContainer cloudBlobContainer = cloudBlobClient.GetContainerReference("interestgroupattachment");
        var blockBlob = cloudBlobContainer.GetBlockBlobReference(filename);

        using (var stream = await blockBlob.OpenWriteAsync())
        using (var zip = new ZipArchive(stream, ZipArchiveMode.Create))
        {
            var files = fileNames;
            foreach (var docfile in fileList)
            {
                using (var fstream = docfile)
                {
                    var entry = zip.CreateEntry(fileNames[counter], CompressionLevel.Optimal);
                    using (var innerFile = entry.Open())
                    {
                        await fstream.CopyToAsync(innerFile);
                    }
                }
                counter++;
            }
        }