How do I create an Excel (.XLS and .XLSX) file in C# without installing Microsoft Office?

To create Excel files (.XLS and .XLSX) in C# without installing Microsoft Office, you can use open-source libraries or Microsoft’s Open XML SDK. Below are the most common and reliable methods:

1. Using the NPOI Library

Supports: .XLS (Excel 97-2003) and .XLSX (Excel 2007+).
License: Apache License 2.0 (free for commercial use).
Steps:

1. Install the NuGet Package:

   Install-Package NPOI

2. Code Example:

   using NPOI.SS.UserModel;
   using NPOI.XSSF.UserModel; // For XLSX
   using NPOI.HSSF.UserModel; // For XLS
   using System.IO;

   public void CreateExcelFile(string filePath, bool isXlsx = true)
   {
       IWorkbook workbook;

       // Create workbook for XLSX or XLS
       if (isXlsx)
           workbook = new XSSFWorkbook();
       else
           workbook = new HSSFWorkbook();

       // Create a worksheet
       ISheet sheet = workbook.CreateSheet("Sheet1");

       // Add data to cells (Row 0, Column 0)
       IRow row = sheet.CreateRow(0);
       row.CreateCell(0).SetCellValue("Hello");
       row.CreateCell(1).SetCellValue("World");

       // Save to file
       using (FileStream fs = new FileStream(filePath, FileMode.Create))
       {
           workbook.Write(fs);
       }
   }

2. Using EPPlus (for .XLSX only)

Supports: .XLSX (Excel 2007+).
License: Polyform Noncommercial License (free for non-commercial use; commercial use requires a license).

1. Install the NuGet Package:

   Install-Package EPPlus

2. Code Example:

   using OfficeOpenXml;
   using System.IO;

   public void CreateExcelFile(string filePath)
   {
       ExcelPackage.LicenseContext = LicenseContext.NonCommercial; // Set license

       using (var package = new ExcelPackage())
       {
           // Add a worksheet
           ExcelWorksheet worksheet = package.Workbook.Worksheets.Add("Sheet1");

           // Add data to cells (Row 1, Column 1)
           worksheet.Cells[1, 1].Value = "Hello";
           worksheet.Cells[1, 2].Value = "World";

           // Save to file
           package.SaveAs(new FileInfo(filePath));
       }
   }

3. Using ClosedXML (for .XLSX only)

Supports: .XLSX (Excel 2007+).
License: MIT License (free for commercial use).

1. Install the NuGet Package:

   Install-Package ClosedXML

2. Code Example:

   using ClosedXML.Excel;
   using System.IO;

   public void CreateExcelFile(string filePath)
   {
       using (var workbook = new XLWorkbook())
       {
           // Add a worksheet
           var worksheet = workbook.Worksheets.Add("Sheet1");

           // Add data to cells (Row 1, Column 1)
           worksheet.Cell(1, 1).Value = "Hello";
           worksheet.Cell(1, 2).Value = "World";

           // Save to file
           workbook.SaveAs(filePath);
       }
   }

4. Using Microsoft’s Open XML SDK (Low-Level)

Supports: .XLSX only.
License: Free (Microsoft’s Open Specification Promise).

1. Install the NuGet Package:

   Install-Package DocumentFormat.OpenXml

2. Code Example:

   using DocumentFormat.OpenXml;
   using DocumentFormat.OpenXml.Packaging;
   using DocumentFormat.OpenXml.Spreadsheet;
   using System.Linq;

   public void CreateExcelFile(string filePath)
   {
       // Create a new spreadsheet document
       using (var document = SpreadsheetDocument.Create(filePath, SpreadsheetDocumentType.Workbook))
       {
           // Add a workbook and worksheet
           WorkbookPart workbookPart = document.AddWorkbookPart();
           workbookPart.Workbook = new Workbook();
           WorksheetPart worksheetPart = workbookPart.AddNewPart<WorksheetPart>();
           worksheetPart.Worksheet = new Worksheet(new SheetData());

           // Add sheets to the workbook
           Sheets sheets = workbookPart.Workbook.AppendChild(new Sheets());
           Sheet sheet = new Sheet()
           {
               Id = workbookPart.GetIdOfPart(worksheetPart),
               SheetId = 1,
               Name = "Sheet1"
           };
           sheets.Append(sheet);

           // Add data to cells
           SheetData sheetData = worksheetPart.Worksheet.GetFirstChild<SheetData>();
           Row row = new Row() { RowIndex = 1 };
           row.Append(
               new Cell() { CellValue = new CellValue("Hello"), DataType = CellValues.String },
               new Cell() { CellValue = new CellValue("World"), DataType = CellValues.String }
           );
           sheetData.Append(row);

           // Save changes
           workbookPart.Workbook.Save();
       }
   }

Comparison

Method	Formats	Ease of Use	License
NPOI	XLS/XLSX	Moderate	Apache 2.0 (Commercial OK)
EPPlus	XLSX	Easy	Non-commercial or Paid
ClosedXML	XLSX	Easy	MIT (Commercial OK)
Open XML SDK	XLSX	Complex	Free (Microsoft)

Recommendation

• Use NPOI if you need .XLS support.
• Use ClosedXML for .XLSX (simplest API).
• Use Open XML SDK for low-level control (advanced use cases).

All methods work without Microsoft Office installed.