SpreadsheetLight for .NET Framework

Open source developer-friendly spreadsheet library compatible with Microsoft Excel 2007/2010/2013 and LibreOffice Calc
SpreadsheetLight is an open source Open XML spreadsheet library for .NET Framework written in C#, and is released under the MIT License. You can create new Open XML spreadsheets, or work with existing Open XML spreadsheets that are compatible with Microsoft Excel 2007/2010/2013 and LibreOffice Calc.