For reading xlsx files there is a library called ClosedXml, based on OpenXml but a bit easier to use. But if you need to read xls files also it won't work.
•Created by The king of kings on 11/12/2022 in #help
❔ Can anyone help me out with a calculation project?
I meant, what is the Swedish for point 5, "5. With a simple rise, calculate the gear back
Don't forget to check the entered values first"? I'm Swedish too.