Following example shows how to open XLS, XLSX, ODS or CSV files by using only the GemBox.Spreadsheet .NET component.

GemBox.Spreadsheet is a C# / VB.NET component that provides a simple and efficient way to read, write, convert, and print native Microsoft Excel (XLSX, XLS) and other spreadsheet (ODS, CSV) formats and various document formats (HTML, PDF, XPS) from .NET applications without the need for Microsoft Excel on either the developer or client machines.
GemBox.Spreadsheet Free is free of charge, while GemBox.Spreadsheet Professional is a commercial version that is licensed per developer.
For more information, see GemBox.Spreadsheet Features or try our examples.

Example opens Excel file (in XLS format) and shows MessageBox with value from cell “A1”:

C# code:

// Load Excel file.
var workbook = ExcelFile.Load("Workbook.xls");

// Select active worksheet.
var worksheet = workbook.Worksheets.ActiveWorksheet;

// Display the value of first cell in MessageBox.
MessageBox.Show(worksheet.Cells["A1"].GetFormattedValue());

Visual Basic .NET code:

' Load Excel file.
Dim workbook = ExcelFile.Load("Workbook.xls")

' Select active worksheet.
Dim worksheet = workbook.Worksheets.ActiveWorksheet

' Display the value of first cell in MessageBox.
MessageBox.Show(worksheet.Cells("A1").GetFormattedValue())