EPPlus VS CsvBenchmarks

Like others, I recommend using the ImportExcel module. It uses and wraps EPPlus Software (EPPlus - Create advanced Excel spreadsheets using .NET (GitHub Project Old / New)) which is a DLL that is included with the ImportExcel PowerShell Module.

There is some additional samples at their old (abandoned) branch: https://github.com/JanKallman/EPPlus/tree/master/SampleApp

Love this version: https://www.nuget.org/packages/EPPlus/4.5.3.3

EPPlus ExcelDataReader NPOI

For reading JSON -> e.g. ServiceStack.Text. For writing into Excel -> Use EPPlus library version 4.5.3.3. This is the last version of EPPlus under the LGPL License (aka free for commercial uses). You can install it using Nuget Package manager: Which library were you using for CSharp?

If you mean library, the older version of EPPlus is still available.

My suggestion would be to avoid using Office Interop. When you use it, it creates a dependency on Office, meaning it has to be installed on the machine in order for your app to run. That's completely unnecessary and wasteful from licensing perspective. There are several packages on Nuget that allow you to work with Excel sheets without the need for Office to be loaded. A couple would be ClosedXML and EPPlus.

The Sylvan.Data.Csv library is also the fastest CSV parser for .NET, and can load data about 3x faster than MTD based on my limited testing.

I don't want to disparage NPOI, because I'm sure it's great for its primary use-case, which is creating/editing spreadsheets. However, from a performance perspective it is one of the slowest libraries for reading Excel data in .NET. Since the OP seemed to be very concerned about performance and only needs to read data, this probably isn't the best choice.

I'm pretty sure NPOI doesn't support .xlsb. At least it didn't the last time I updated my benchmarks: https://github.com/MarkPflug/Benchmarks/blob/main/docs/ExcelBenchmarks.md

If you're trying to load an Excel worksheet into a DataTable, I maintain a library that can make this quite easy: Sylvan.Data.Excel. It is available as a nuget package, open source, MIT licensed, and the fastest Excel reader for .NET.

I maintain a library, Sylvan.Data.Excel that might work for you. I claim it is the fastest Excel library in the .NET ecosystem. It is open source and MIT licensed, so feel free to use it however you wish. It has no external dependencies other than .NET itself.

It provides a forward only data reader (DbDataReader) for all common excel formats (.xlsx, .xlsb, and .xls). It is the fastest and lowest allocating Excel reader in the .NET ecosystem.

This one is one that I personally maintain: Sylvan.Data.Excel It isn't fully featured, but it is the fastest that I'm aware of.

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.

It isn't exactly a full-featured library, but it is cross-platform and is the fastest and lowest allocating Excel reader that I'm aware of for .NET. That might not be a huge concern if you're just processing the occasional file.

Thanks for this -- I've pushed a PR that corrects a slight incorrectness issue that biased the results in Cursively's favor, uses the original byte array directly instead of needlessly wrapping it in a MemoryStream, and uses the same optimization that you used to make SylvanSimplePool win in its category. CursivelyCsv is now the winner on my machine in this category when doPooling is on.