ExcelWriter is a .NET library and API. It allows you to generate, manipulate, and read Excel documents from your own applications. You can use ExcelWriter to process workbooks with a fully programmatic object model, or design report templates in Office and quickly merge them with data. ExcelWriter can generate spreadsheets in Microsoft Excel format (.xls) or Office Open XML format (.xlsx) and it will preserve all of the familiar features associated with Excel workbooks.
ExcelWriter comes in two editions, depending on the functionality needed for your application.