EasyXLS is an Excel library that it used to create Excel files, format data in cells using predefined formats or user-defined formats.
The Excel file can be created without MS Excel installed and without Office Interop.
The library has three versions:
EasyXLS version for .NET lets you create Excel file from ASP.NET, WinForms or console applications.
EasyXLS version for Java lets you create Excel file from servlets, JSF and any Java application.
The library permits the creation of Excel files in XLSX, XLS, XLSM and XLSB file formats for Microsoft Excel 97, 2003, 2007, 2010 and 2013. The Excel workbook can have multiple sheets.
For source code samples in any of the mentioned programming languages and more technical details, check this link about how to create Excel files. You may also find samples about how to create Excel file from basic data structures like lists, DataTable, DataSet, GridView, DataGridView or ResultSet.