Hi,
You can only read the worksheets concurrently, so this should work for you.
However, I conducted a benchmark comparison between the regular List<List<string>> and concurrent ConcurrentBag<List<string>> reading to evaluate their performance.
While concurrent processing does show a slight performance improvement (approximately 4–8%), the difference is relatively small. Also, the actual performance gain varies depending on the structure and size of the processed Excel files.
Anyway, I hope this helps, let me know if you need anything else.
Regards,
Mario