ASP.NET Export to Excel: Best Tool Comparison for C# Developers

What Are the Common Methods to Export Data to Excel in ASP.NET Core?

The simplest way to export data involves several distinct approaches. Most workflows begin by establishing a connection string to retrieve data before choosing an export path.

• Traditional MIME Type Approach: This legacy method uses the Content Type property (set to application/vnd.ms-excel) and streams HTML content to the browser. While it works as a default solution in older systems, it often triggers format warnings.

• Library-Based Solutions: Modern libraries require adding NuGet references to generate genuine XLSX files using the Open XML format. These include IronXL, ClosedXML, and EPPlus, which provide APIs to create workbook objects and save files with proper formatting.

  Feature	MIME Type/HTML	ClosedXML	EPPlus	IronXL
  Genuine XLSX Output	No	Yes	Yes	Yes
  CSV File Support	Manual	Limited	Limited	Native
  No Excel Warning	No	Yes	Yes	Yes
  Formula Support	No	Yes	Yes	Yes
  JSON/XML Export	No	No	No	Yes
  Commercial License	N/A	MIT	Polyform	Commercial
  .NET Core Support	Yes	Yes	Yes	Yes

How Does the Traditional GridView Export Approach Work?

In legacy WebForms and some older MVC patterns, developers often export GridView data by rendering it as HTML. The application uses Response.AddHeader to define the filename and then proceeds to write the HTML stream directly to the output.

// Traditional approach - exports HTML disguised as Excel
public void ExportToExcel(object sender, EventArgs e)
{
    Response.Clear();
    Response.Buffer = true;
    Response.ContentType = "application/vnd.ms-excel";
    Response.AddHeader("content-disposition", "attachment;filename=Report.xls");
    StringWriter stringWriter = new StringWriter();
    HtmlTextWriter htmlTextWriter = new HtmlTextWriter(stringWriter);
    // Render grid content as HTML
    DataGrid1.RenderControl(htmlTextWriter);
    Response.Write(stringWriter.ToString());
    Response.End();
}
public override void VerifyRenderingInServerForm(Control control)
{
    // Required to prevent server form rendering errors
}

// Traditional approach - exports HTML disguised as Excel
public void ExportToExcel(object sender, EventArgs e)
{
    Response.Clear();
    Response.Buffer = true;
    Response.ContentType = "application/vnd.ms-excel";
    Response.AddHeader("content-disposition", "attachment;filename=Report.xls");
    StringWriter stringWriter = new StringWriter();
    HtmlTextWriter htmlTextWriter = new HtmlTextWriter(stringWriter);
    // Render grid content as HTML
    DataGrid1.RenderControl(htmlTextWriter);
    Response.Write(stringWriter.ToString());
    Response.End();
}
public override void VerifyRenderingInServerForm(Control control)
{
    // Required to prevent server form rendering errors
}

IRON VB CONVERTER ERROR developers@ironsoftware.com

How Does IronXL Simplify Excel File Generation in ASP.NET Core?

IronXL provides a modern API for creating genuine Excel files without Microsoft Office dependencies. It allows users to trigger a download from the same page without interrupting the user experience. The following example demonstrates how to export data to an Excel document and stream it to the user's browser:

using IronXL;
using Microsoft.AspNetCore.Mvc;
public class ExportController : Controller
{
    [HttpPost]
    public IActionResult ExportReport()
    {
        // Create workbook and worksheet
        WorkBook workbook = WorkBook.Create(ExcelFileFormat.XLSX);
        WorkSheet worksheet = workbook.CreateWorkSheet("Sales Data");
        // Add header row
        worksheet["A1"].Value = "Product";
        worksheet["B1"].Value = "Quantity";
        worksheet["C1"].Value = "Revenue";
        // Populate data rows from your data source
        worksheet["A2"].Value = "Widget A";
        worksheet["B2"].Value = 150;
        worksheet["C2"].Value = 4500.00;
        worksheet["A3"].Value = "Widget B";
        worksheet["B3"].Value = 230;
        worksheet["C3"].Value = 6900.00;
        // Style the header cells
        var headerRange = worksheet["A1:C1"];
        headerRange.Style.Font.Bold = true;
        // Generate file for browser download
        byte[] fileBytes = workbook.ToByteArray();
        string filename = $"SalesReport_{DateTime.Now:yyyyMMdd}.xlsx";
        return File(fileBytes,
            "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
            filename);
    }
}

using IronXL;
using Microsoft.AspNetCore.Mvc;
public class ExportController : Controller
{
    [HttpPost]
    public IActionResult ExportReport()
    {
        // Create workbook and worksheet
        WorkBook workbook = WorkBook.Create(ExcelFileFormat.XLSX);
        WorkSheet worksheet = workbook.CreateWorkSheet("Sales Data");
        // Add header row
        worksheet["A1"].Value = "Product";
        worksheet["B1"].Value = "Quantity";
        worksheet["C1"].Value = "Revenue";
        // Populate data rows from your data source
        worksheet["A2"].Value = "Widget A";
        worksheet["B2"].Value = 150;
        worksheet["C2"].Value = 4500.00;
        worksheet["A3"].Value = "Widget B";
        worksheet["B3"].Value = 230;
        worksheet["C3"].Value = 6900.00;
        // Style the header cells
        var headerRange = worksheet["A1:C1"];
        headerRange.Style.Font.Bold = true;
        // Generate file for browser download
        byte[] fileBytes = workbook.ToByteArray();
        string filename = $"SalesReport_{DateTime.Now:yyyyMMdd}.xlsx";
        return File(fileBytes,
            "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
            filename);
    }
}

IRON VB CONVERTER ERROR developers@ironsoftware.com

// Export as CSV file instead of XLSX
workbook.SaveAsCsv("output.csv");

// Export as CSV file instead of XLSX
workbook.SaveAsCsv("output.csv");

IRON VB CONVERTER ERROR developers@ironsoftware.com

How Do ClosedXML and EPPlus Compare?

ClosedXML wraps Microsoft's Open XML SDK with a user-friendly API. In Solution Explorer, install via NuGet with Install-Package ClosedXML:

using ClosedXML.Excel;
public IActionResult ExportWithClosedXML()
{
    using var workbook = new XLWorkbook();
    var worksheet = workbook.AddWorksheet("Data");
    worksheet.Cell(1, 1).Value = "Name";
    worksheet.Cell(1, 2).Value = "Amount";
    using var stream = new MemoryStream();
    workbook.SaveAs(stream);
    return File(stream.ToArray(),
        "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
        "export.xlsx");
}

using ClosedXML.Excel;
public IActionResult ExportWithClosedXML()
{
    using var workbook = new XLWorkbook();
    var worksheet = workbook.AddWorksheet("Data");
    worksheet.Cell(1, 1).Value = "Name";
    worksheet.Cell(1, 2).Value = "Amount";
    using var stream = new MemoryStream();
    workbook.SaveAs(stream);
    return File(stream.ToArray(),
        "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
        "export.xlsx");
}

IRON VB CONVERTER ERROR developers@ironsoftware.com

Which Library Should Developers Choose for Excel Export?

For ASP.NET Core applications requiring Excel export, library selection depends on project requirements:

Choose IronXL when: Needing multi-format support (XLSX, CSV file, JSON, XML), requiring professional support, or building commercial applications needing guaranteed compatibility with complex Excel features within ASP projects.

Choose ClosedXML when: Building open-source projects requiring MIT licensing with basic Excel file generation.

Choose EPPlus when: Existing projects already use EPPlus, and the migration cost outweighs licensing considerations.

Summary

Implementing ASP.NET export to Excel functionality requires choosing between legacy HTML-based methods and modern library solutions. At the same time, the traditional MIME type approach using the new HtmlTextWriter and Response.AddHeader for content-disposition creates functional downloads, but the exported file format triggers warnings and lacks true Excel features.

IronXL delivers genuine Excel file generation with multiple output formats, intuitive worksheet and workbook management, and proper handling of data rows and cells. The library eliminates void VerifyRenderingInServerForm overrides and object sender, EventArgs e patterns from legacy code.

For implementation guidance, refer to the IronXL documentation and code examples. Purchase a license to deploy IronXL in production and generate professional Excel documents your users can download from the browser.

Get stated with IronXL now.

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