EPPlus VS Sylvan

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.

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.