NPOI VS Sylvan

NPOI (Open source, MIT)

For .NET Core you can use - https://github.com/nissl-lab/npoi - https://github.com/Jetro223/DocXNETCore

I use NPOI https://github.com/nissl-lab/npoi its a popular package for reading Excel. It is both faster than interop and free (open source).

Have you tried NPOI?

Competitor#2 (NPOI - v2.5.6)

If you are trying to *create* Excel files, then you might take a look at [NPOI](https://github.com/nissl-lab/npoi) which is also open source with a permissive license. There is also [ClosedXml](https://github.com/ClosedXML/ClosedXML), which has these capabilities.

I'd like to use NPOI to deal with Excel files. It's open source and you don't have to install Microsoft Office.

EPPlus ExcelDataReader NPOI

A while back I needed to process CSV with millions of records in a timescale of seconds. Sylvan Data was the best fit in terms of speed and memory efficiency. It might help you. https://github.com/MarkPflug/Sylvan

I maintain a couple libraries that aim to provide similar functionality to MTD: Sylvan.Data and Sylvan.Data.Csv.

Here is a simple, complete gist showing how to turn a DbDataReader into an HTML table. The WriteHtmlTable extension method can be used with any ADO.NET compatible driver, which the Sylvan.Data.Excel and Sylvan.Data.Csv libraries both support.

I maintain a couple libraries that can help with reading the data files: Sylvan.Data.Csv and Sylvan.Data.Excel. I see no reason to not allow users to provide whichever format is convenient for them.

I maintain a CSV library, Sylvan.Data.Csv, that shouldn't have any issue parsing this. You'll need to explicitly specify that space (' ') is the delimiter.

Here is a some sample code of how to echo the contents of an Excel spreadsheet as CSV to the client browser using my libraries Sylvan.Data.Excel and Sylvan.Data.Csv:

``` For reference, my implementation is here.

I maintain a couple libraries that should make this quite easy: Sylvan.Data.Csv, and Sylvan.Data.Excel. They are both open-source and MIT licensed. They are also both fastest-in-class at their particular tast.

Personally, I'd recommend Sylvan.Data.Csv, but being the author I'm probably a bit biased. Here is some CSV performance analysis that Joel Verhagen did for .NET libraries recently.