Handling Excel files in NAV 2013 (including R2) is not as easy as it seems at first. The Excel Buffer table – an obvious choice of the old days – supports only Open XML format (*.xlsx), and Excel Interoperability implementation seems a bit buggy (check the comments in my old post about .NET interoperability: https://vjeko.com/blog/the-beauty-and-the-beast-nav-and-net). You can still use automation, but then you must handle everything, or at least most of it, on the client end. And, to make it all just a bit worse, none of these approaches, even when they work, will impress you with their speed. All in all, if you want to handle legacy Excel files (*.xls) you will have to make some compromises.
Last week, Mark asked me for a bit of help on a project where he had to import *.xls files into NAV 2013, and he hit all of the possible walls provided by the Excel Buffer, .NET Interoperability components for Excel, and automation walls possible.
When I gave Mark my solution, he said: you should blog about this. So, here I am, blogging about a simple way to read data from Excel, any version, lightning fast.