How to Create Excel Files in C#: Interop vs IronXL

Introduction

Creating Excel files programmatically is a fundamental requirement in many C# applications. While Microsoft.Office.Interop.The traditional approach to creating Excel files in C# using Interop has been Excel. However, it comes with limitations, such as requiring Microsoft Excel to be installed and relying on Primary Interop Assemblies. Modern Excel library alternatives like IronXL allow you to create an Excel workbook, work with multiple worksheets, and generate XLSX or CSV files without Microsoft Office. This article compares how different libraries handle Excel file creation, providing sample code and guidance for .NET developers.

Quick Comparison Overview

Note: “Excel Interop” requires Microsoft Excel to be installed, along with the Primary Interop Assembly. Alternative libraries, such as IronXL, allow you to create Excel files, workbooks, and worksheets without requiring Office, and support xlsx files, CSV files, and multiple worksheets.

Why Move Beyond Excel Interop?

Microsoft.Office.Interop.Excel alternatives are essential because Excel Interop requires Microsoft Excel installed on every machine where your application runs. This dependency creates deployment challenges, especially for server environments where Microsoft explicitly warns against Office automation. Using Interop without Excel results in exceptions, warning messages, or failed attempts to create an Excel document programmatically. Applications also suffer from COM dependency issues, version conflicts, and poor performance due to Excel running as a background process.

Modern Excel libraries, such as IronXL, eliminate these issues. You can create Excel files, write data to worksheets, generate CSV or XML files, and work with new Excel workbooks without relying on Office, the Excel application object, or the Primary Interop Assembly. Developers can also use Visual Studio, Visual Basic, or console application projects to implement Excel automation across Windows or cross-platform environments.

Get started with IronXL's free trial to eliminate these dependencies entirely.

Creating Excel Files with Interop

Let's first look at the traditional approach using Excel Interop:

using Excel = Microsoft.Office.Interop.Excel;
// Create Excel application instance
Excel.Application excelApp = new Excel.Application();
Excel.Workbook workbook = excelApp.Workbooks.Add();
Excel.Worksheet worksheet = (Excel.Worksheet)workbook.Sheets[1];
// Add data to cells
worksheet.Cells[1, 1] = "Product";
worksheet.Cells[1, 2] = "Price";
worksheet.Cells[2, 1] = "Widget";
worksheet.Cells[2, 2] = 9.99;
// Save and cleanup
workbook.SaveAs(@"C:\temp\products.xlsx");
workbook.Close();
excelApp.Quit();
// Release COM objects
System.Runtime.InteropServices.Marshal.ReleaseComObject(worksheet);
System.Runtime.InteropServices.Marshal.ReleaseComObject(workbook);
System.Runtime.InteropServices.Marshal.ReleaseComObject(excelApp);

using Excel = Microsoft.Office.Interop.Excel;
// Create Excel application instance
Excel.Application excelApp = new Excel.Application();
Excel.Workbook workbook = excelApp.Workbooks.Add();
Excel.Worksheet worksheet = (Excel.Worksheet)workbook.Sheets[1];
// Add data to cells
worksheet.Cells[1, 1] = "Product";
worksheet.Cells[1, 2] = "Price";
worksheet.Cells[2, 1] = "Widget";
worksheet.Cells[2, 2] = 9.99;
// Save and cleanup
workbook.SaveAs(@"C:\temp\products.xlsx");
workbook.Close();
excelApp.Quit();
// Release COM objects
System.Runtime.InteropServices.Marshal.ReleaseComObject(worksheet);
System.Runtime.InteropServices.Marshal.ReleaseComObject(workbook);
System.Runtime.InteropServices.Marshal.ReleaseComObject(excelApp);

IRON VB CONVERTER ERROR developers@ironsoftware.com

This code requires Excel installation, manual COM object cleanup, and won't work on non-Windows platforms. The complexity increases when handling multiple worksheets, saving to different file formats, or working in a server environment. This is why many developers look for an Excel library that does not require Microsoft Office.

How Does IronXL Compare?

IronXL eliminates these complications with a modern, intuitive API for Excel automation without Microsoft Office:

using IronXL;
// Create workbook without Excel
WorkBook workbook = WorkBook.Create();
WorkSheet worksheet = workbook.CreateWorkSheet("Products");
// Add data using familiar syntax
worksheet["A1"].Value = "Product";
worksheet["B1"].Value = "Price";
worksheet["A2"].Value = "Widget";
worksheet["B2"].Value = 9.99;
// Apply formatting
worksheet["A1:B1"].Style.Font.Bold = true;
worksheet["B2"].FormatString = "$#,###";
// Save with one line
workbook.SaveAs("products.xlsx");

using IronXL;
// Create workbook without Excel
WorkBook workbook = WorkBook.Create();
WorkSheet worksheet = workbook.CreateWorkSheet("Products");
// Add data using familiar syntax
worksheet["A1"].Value = "Product";
worksheet["B1"].Value = "Price";
worksheet["A2"].Value = "Widget";
worksheet["B2"].Value = 9.99;
// Apply formatting
worksheet["A1:B1"].Style.Font.Bold = true;
worksheet["B2"].FormatString = "$#,###";
// Save with one line
workbook.SaveAs("products.xlsx");

IRON VB CONVERTER ERROR developers@ironsoftware.com

IronXL allows you to create an Excel file, new workbook, and multiple worksheets programmatically. You can write data, display data, and handle XLS, XLSX, CSV, or XML files without Microsoft Excel installed or referencing the Primary Interop Assembly. This makes it a fully managed Excel library suitable for .NET Framework, .NET Core, console applications, and cross-platform environments.

Because IronXL is available via NuGet package, you can add it directly to your Visual Studio project without worrying about installing Microsoft Office. There’s no need to manage the Excel application object or release COM objects manually, reducing the risk of exceptions or warning messages. Learn more about creating Excel files with IronXL or explore Excel formulas and calculations.

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How Do Other Libraries Compare?

using OfficeOpenXml;
// Set license context (required from v5+)
ExcelPackage.License.SetNonCommercialPersonal("Test");
using (var package = new ExcelPackage())
{
    var worksheet = package.Workbook.Worksheets.Add("Products");
    worksheet.Cells[1, 1].Value = "Product";
    worksheet.Cells[1, 2].Value = "Price";
    worksheet.Cells[2, 1].Value = "Widget";
    worksheet.Cells[2, 2].Value = 9.99;
    package.SaveAs(new FileInfo("products.xlsx"));
}

using OfficeOpenXml;
// Set license context (required from v5+)
ExcelPackage.License.SetNonCommercialPersonal("Test");
using (var package = new ExcelPackage())
{
    var worksheet = package.Workbook.Worksheets.Add("Products");
    worksheet.Cells[1, 1].Value = "Product";
    worksheet.Cells[1, 2].Value = "Price";
    worksheet.Cells[2, 1].Value = "Widget";
    worksheet.Cells[2, 2].Value = 9.99;
    package.SaveAs(new FileInfo("products.xlsx"));
}

IRON VB CONVERTER ERROR developers@ironsoftware.com

using ClosedXML.Excel;
using (var workbook = new XLWorkbook())
{
    var worksheet = workbook.Worksheets.Add("Products");
    worksheet.Cell("A1").Value = "Product";
    worksheet.Cell("B1").Value = "Price";
    worksheet.Cell("A2").Value = "Widget";
    worksheet.Cell("B2").Value = 9.99;
    workbook.SaveAs("products.xlsx");
}

using ClosedXML.Excel;
using (var workbook = new XLWorkbook())
{
    var worksheet = workbook.Worksheets.Add("Products");
    worksheet.Cell("A1").Value = "Product";
    worksheet.Cell("B1").Value = "Price";
    worksheet.Cell("A2").Value = "Widget";
    worksheet.Cell("B2").Value = 9.99;
    workbook.SaveAs("products.xlsx");
}

IRON VB CONVERTER ERROR developers@ironsoftware.com

using NPOI.SS.UserModel;
using NPOI.XSSF.UserModel;
IWorkbook workbook = new XSSFWorkbook();
ISheet worksheet = workbook.CreateSheet("Products");
IRow headerRow = worksheet.CreateRow(0);
headerRow.CreateCell(0).SetCellValue("Product");
headerRow.CreateCell(1).SetCellValue("Price");
IRow dataRow = worksheet.CreateRow(1);
dataRow.CreateCell(0).SetCellValue("Widget");
dataRow.CreateCell(1).SetCellValue(9.99);
using (FileStream file = new FileStream("products.xlsx", FileMode.Create))
{
    workbook.Write(file);
}

using NPOI.SS.UserModel;
using NPOI.XSSF.UserModel;
IWorkbook workbook = new XSSFWorkbook();
ISheet worksheet = workbook.CreateSheet("Products");
IRow headerRow = worksheet.CreateRow(0);
headerRow.CreateCell(0).SetCellValue("Product");
headerRow.CreateCell(1).SetCellValue("Price");
IRow dataRow = worksheet.CreateRow(1);
dataRow.CreateCell(0).SetCellValue("Widget");
dataRow.CreateCell(1).SetCellValue(9.99);
using (FileStream file = new FileStream("products.xlsx", FileMode.Create))
{
    workbook.Write(file);
}

IRON VB CONVERTER ERROR developers@ironsoftware.com

Key Decision Factors

Migration from Interop to IronXL

Migrating from Excel Interop to IronXL follows a straightforward pattern. For detailed guidance, see the IronXL documentation and explore code examples:

1. Remove COM references - Replace Microsoft.Office.Interop.Excel references with IronXL
2. Simplify object creation - Replace Application/Workbook/Worksheet hierarchy with direct WorkBook creation
3. Update cell access - Convert from Cells[row, col] to worksheet["A1"] notation
4. Remove cleanup code - Eliminate Marshal.ReleaseComObject calls
5. Test cross-platform - Verify functionality on target deployment platforms

For complex migrations involving Excel charts or conditional formatting, IronXL provides comprehensive support.

Understanding the Limitations

It's important to note that Primary Interop Assemblies (PIAs) cannot function without Excel installed—they're merely interfaces to COM objects that require the actual Office application. This misconception often leads to deployment failures when moving applications to servers or attempting Excel automation without Office installation.

Regarding security, IronXL undergoes regular security audits and maintains DigiCert certification, providing enterprise-grade protection without the vulnerabilities associated with COM interfaces. For detailed security information, visit the IronXL security documentation.

Conclusion

While Excel Interop served its purpose in desktop applications, modern development demands more flexible alternatives to the Excel library. IronXL provides the most comprehensive alternative for creating Excel files without Interop, combining ease of use with enterprise features and cross-platform Excel support.

Whether you're building cloud applications, working with Docker containers, or developing cross-platform solutions, selecting a library that doesn't require Excel installation is crucial for creating scalable and maintainable applications. Download IronXL to transform your Excel automation workflow today.

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