I know that my question will be very similar to other ones already asked on SO but as I can't find a satisfying answer, I try my luck !
Does so know whether it's possible or not to generate charts in an Excel spreadsheet using the NPOI library.
I have read that blog but it gives an example where there is already an existing template. Isn't it possible "from scratch" ?
After more investigation I got my answer here: http://npoi.codeplex.com/releases/view/19351
Unsupported Features: Excel Chart
so as explained by Leniel in his blog, we need to use a primary spreadsheet as a template.
Thanks a lot Leniel ! :)