Read Excel File Using Microsoft Office Interop Excel C#: And a Faster Way to Create Excel Files Without Office

How Does the Interop Library Create an Excel Workbook?

The Microsoft.Office.Interop.Excel namespace exposes the same COM object model that Excel uses internally. To read or create Excel files through this interop library, you first instantiate an Application object, add a new workbook to its Workbooks collection, and then access individual worksheet cells. The following example demonstrates a minimal console application using Microsoft.Office.Interop.Excel to create an XLSX file and write values into cells.

using Excel = Microsoft.Office.Interop.Excel;
using System.Runtime.InteropServices;
// Create the Excel Application COM object
Excel.Application excelApp = new Excel.Application();
if (excelApp == null)
{
    Console.WriteLine("Error: Excel is not properly installed.");
    return;
}
// Add a new workbook and access the default worksheet
Excel.Workbook xlWorkBook = excelApp.Workbooks.Add(Type.Missing);
Excel.Worksheet xlWorkSheet = (Excel.Worksheet)xlWorkBook.ActiveSheet;
// Write data into specific cells
xlWorkSheet.Cells[1, 1] = "Product";
xlWorkSheet.Cells[1, 2] = "Price";
xlWorkSheet.Cells[2, 1] = "Widget";
xlWorkSheet.Cells[2, 2] = "29.99";
// Save as an XLSX file and clean up COM objects
string filepath = @"C:\Reports\products.xlsx";
xlWorkBook.SaveAs(filepath);
xlWorkBook.Close(false);
excelApp.Quit();
// Release every COM object to prevent orphaned Excel processes
Marshal.ReleaseComObject(xlWorkSheet);
Marshal.ReleaseComObject(xlWorkBook);
Marshal.ReleaseComObject(excelApp);

using Excel = Microsoft.Office.Interop.Excel;
using System.Runtime.InteropServices;
// Create the Excel Application COM object
Excel.Application excelApp = new Excel.Application();
if (excelApp == null)
{
    Console.WriteLine("Error: Excel is not properly installed.");
    return;
}
// Add a new workbook and access the default worksheet
Excel.Workbook xlWorkBook = excelApp.Workbooks.Add(Type.Missing);
Excel.Worksheet xlWorkSheet = (Excel.Worksheet)xlWorkBook.ActiveSheet;
// Write data into specific cells
xlWorkSheet.Cells[1, 1] = "Product";
xlWorkSheet.Cells[1, 2] = "Price";
xlWorkSheet.Cells[2, 1] = "Widget";
xlWorkSheet.Cells[2, 2] = "29.99";
// Save as an XLSX file and clean up COM objects
string filepath = @"C:\Reports\products.xlsx";
xlWorkBook.SaveAs(filepath);
xlWorkBook.Close(false);
excelApp.Quit();
// Release every COM object to prevent orphaned Excel processes
Marshal.ReleaseComObject(xlWorkSheet);
Marshal.ReleaseComObject(xlWorkBook);
Marshal.ReleaseComObject(excelApp);

The above code creates an Excel workbook, populates a worksheet with row and cell values, saves the file, and then manually releases each COM object. That cleanup at the end isn't optional — skip it, and you'll find ghost EXCEL.EXE processes consuming memory on your system. Notice, too, that the code checks whether the Application object is null; if Microsoft Office isn't installed, every line after that will throw an error. The same version of the Office interop library must match the version of Office on the machine, or you'll face FileNotFoundException and similar runtime errors that are notoriously difficult to debug.

Visual Basic developers encounter the same challenges when using Excel Microsoft.Office.Interop.Excel, because the underlying COM infrastructure is identical across .NET languages.

What Problems Does the Interop Approach Cause on Servers and in the Cloud?

Microsoft explicitly discourages using Office Interop on server environments. The interop library launches a full instance of the Excel application behind the scenes, that means every request on a web server or cloud app spins up a hidden Windows desktop process. On a Linux server, it won't work at all. Connection strings to databases, file system paths, and user permissions all become additional points of failure when Office isn't installed or when different versions of Microsoft Office conflict with each other.

Developers frequently post about these issues on Stack Overflow and Microsoft Q&A, searching for ways to read Excel files and create Excel files without having Excel installed. The table below summarizes the key differences.

| Feature | Office Interop | IronXL | | --- | --- | --- | | Requires Excel installed | Yes — only the developer machine and every production server | No | | Supported Excel file formats | XLS, XLSX | XLS, XLSX, CSV, TSV, JSON, XML | | Cross-platform (.NET Core, Linux, macOS) | Windows only | Windows, Linux, macOS, Azure | | COM object cleanup required | Yes — manual Marshal.ReleaseComObject | No | | Server / cloud deployment | Not recommended by Microsoft | Fully supported | | Performance | Slower — launches hidden Excel process | Better performance — managed .NET code | | .NET Framework & .NET Core support | .NET Framework only | .NET Framework, .NET Core, .NET 5–10 |

How Can Excel Files Be Created Without Microsoft Office Installed?

IronXL is a .NET Excel library that reads, writes, and creates Excel files entirely in managed code. There's no dependency on Microsoft Office, no COM object to release, and no version conflicts to debug. Install it via NuGet in Visual Studio using the Solution Explorer, search for IronXL.Excel, and you're ready to go. It works fine across .NET Framework 4.6.2+, .NET Core, and .NET 5 through .NET 10 on all major operating systems.

using IronXL;
// Create a new Excel workbook — default value is XLSX format
WorkBook workBook = WorkBook.Create(ExcelFileFormat.XLSX);
// Add a worksheet and populate cells with data
WorkSheet workSheet = workBook.CreateWorkSheet("Sales");
workSheet["A1"].Value = "Product";
workSheet["B1"].Value = "Price";
workSheet["A2"].Value = "Widget";
workSheet["B2"].Value = 29.99;
// Apply basic formatting
workSheet["A1"].Style.Font.Bold = true;
workSheet["B1"].Style.Font.Bold = true;
// Save the XLSX file
workBook.SaveAs(@"C:\Reports\products.xlsx");

using IronXL;
// Create a new Excel workbook — default value is XLSX format
WorkBook workBook = WorkBook.Create(ExcelFileFormat.XLSX);
// Add a worksheet and populate cells with data
WorkSheet workSheet = workBook.CreateWorkSheet("Sales");
workSheet["A1"].Value = "Product";
workSheet["B1"].Value = "Price";
workSheet["A2"].Value = "Widget";
workSheet["B2"].Value = 29.99;
// Apply basic formatting
workSheet["A1"].Style.Font.Bold = true;
workSheet["B1"].Style.Font.Bold = true;
// Save the XLSX file
workBook.SaveAs(@"C:\Reports\products.xlsx");

How Can Worksheet Data Be Read and Written Across Rows and Cells?

Reading existing Excel files is just as straightforward. The WorkBook.Load method accepts a string filepath to any XLS, XLSX, or CSV file. From there, each worksheet exposes its rows and cells as iterable collections, making it simple to read data, modify values, or upload results to a database or server endpoint.

using IronXL;
// Load an existing Excel file
WorkBook workBook = WorkBook.Load(@"C:\Reports\products.xlsx");
WorkSheet workSheet = workBook.DefaultWorkSheet;
// Read and display each row of data
foreach (var row in workSheet.Rows)
{
    foreach (var cell in row.ToArray())
    {
        Console.Write(cell.Value + "\t");
    }
    Console.WriteLine();
}
// Update a specific cell and save
workSheet["B2"].Value = 34.99;
workBook.SaveAs(@"C:\Reports\products_updated.xlsx");

using IronXL;
// Load an existing Excel file
WorkBook workBook = WorkBook.Load(@"C:\Reports\products.xlsx");
WorkSheet workSheet = workBook.DefaultWorkSheet;
// Read and display each row of data
foreach (var row in workSheet.Rows)
{
    foreach (var cell in row.ToArray())
    {
        Console.Write(cell.Value + "\t");
    }
    Console.WriteLine();
}
// Update a specific cell and save
workSheet["B2"].Value = 34.99;
workBook.SaveAs(@"C:\Reports\products_updated.xlsx");

What's the Best Path Forward for .NET Excel Automation?

If a project is locked to a legacy Windows desktop environment where Microsoft Office is already installed and the same version will remain stable, the interop library can work fine for basic tasks. But for everything else, server deployments, cloud apps, cross-platform builds, or any scenario where you want better performance and fewer runtime errors, a standalone .NET Excel library is the clear choice.

IronXL handles every common Excel operation (creating workbooks, reading Excel spreadsheet data, writing to cells, saving across multiple file extension types including XLS and XLSX) through a clean, modern API that runs everywhere .NET runs. It supports both C# and Visual Basic projects, and the same code works on Windows, Linux, and macOS without modification.

Start a free 30-day trial to test it in your own project, or explore licensing options when you're ready to deploy.