Best: ...😓...

Worst: having to deal with excel data import in C# in a server environment without drivers for working with excel files 🤐

@jAsE trust me, you'll lose your mind, because Microsoft seems to have never thought of automating excel, and the official drivers (DB drivers) are far from perfect (aka random data loss as a feature)

Hello my friend. Let me show you the wonders of ClosedXml!

@Firedragonweb nice for excel 2007+, but I had the request to support .xls too (2003) which is binary format 😔

I was going to promote openxml but it looks like closedxml is the follow-up?

In that case you're kind of out of luck :/

@ArcaneEye unfortunately, the client doesn't want to be bothered to press "Save As..." button in Excel 😥

@ArcaneEye today I tried two libraries (EPPLUS and NPOI, the latter is better because of the support for the old format .xls(2003)) that seems promising and working. If I can get those libraries to include in the main old project without issues, they go to production! :D
Plus point: they are more reliable against data loss (none, from my tests) than the Microsoft old db drivers that can read through those files.