How to Export Excel Files in Blazor Using IronXL

Creating the Blazor Server Project

Start by creating a new Blazor Server project in Visual Studio 2022 or later, targeting .NET 10. Once the project is ready, install IronXL through the NuGet Package Manager Console:

Install-Package IronXL.Excel

IronXL works with .NET 6 and later, so existing Blazor projects can adopt it without upgrading the framework. For alternative installation methods -- such as the NuGet UI or CLI -- see the IronXL installation guide.

Adding the JavaScript Download Helper

Blazor Server runs on the server side, so triggering a file download requires a small JavaScript bridge. In your wwwroot folder, add a file called excelExport.js:

window.downloadFileFromStream = async (fileName, contentStreamReference) => {
    const arrayBuffer = await contentStreamReference.arrayBuffer();
    const blob = new Blob([arrayBuffer]);
    const url = URL.createObjectURL(blob);
    const anchorElement = document.createElement('a');
    anchorElement.href = url;
    anchorElement.download = fileName ?? 'export.xlsx';
    anchorElement.click();
    anchorElement.remove();
    URL.revokeObjectURL(url);
}

window.downloadFileFromStream = async (fileName, contentStreamReference) => {
    const arrayBuffer = await contentStreamReference.arrayBuffer();
    const blob = new Blob([arrayBuffer]);
    const url = URL.createObjectURL(blob);
    const anchorElement = document.createElement('a');
    anchorElement.href = url;
    anchorElement.download = fileName ?? 'export.xlsx';
    anchorElement.click();
    anchorElement.remove();
    URL.revokeObjectURL(url);
}

Include this script in your _Host.cshtml file (or App.razor in .NET 8+):

<script src="~/excelExport.js"></script>

<script src="~/excelExport.js"></script>

This function converts the byte stream from Blazor into a temporary blob URL, triggers the browser download, then cleans up the URL object to prevent memory leaks. It is intentionally minimal -- the heavy lifting happens in C# on the server.

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Building the ExcelExportService

Create a new file Services/ExcelExportService.cs:

using IronXL;
using System.IO;
using ExportExcel.Models;

public class ExcelExportService
{
    public byte[] GenerateSalesReport(List<SalesData> salesData)
    {
        var workbook = WorkBook.Create(ExcelFileFormat.XLSX);
        workbook.Metadata.Author = "Sales Department";

        var worksheet = workbook.CreateWorkSheet("Monthly Sales");

        // Add column headers
        worksheet["A1"].Value = "Date";
        worksheet["B1"].Value = "Product";
        worksheet["C1"].Value = "Quantity";
        worksheet["D1"].Value = "Revenue";
        worksheet["E1"].Value = "Profit Margin";

        // Style the header row
        var headerRange = worksheet["A1:E1"];
        headerRange.Style.Font.Bold = true;
        headerRange.Style.BackgroundColor = "#4472C4";
        headerRange.Style.Font.Color = "#FFFFFF";

        // Populate data rows
        int row = 2;
        foreach (var sale in salesData)
        {
            worksheet[$"A{row}"].Value = sale.Date.ToString("yyyy-MM-dd");
            worksheet[$"B{row}"].Value = sale.Product ?? "Unknown";
            worksheet[$"C{row}"].Value = sale.Quantity;
            worksheet[$"D{row}"].Value = sale.Revenue;
            worksheet[$"E{row}"].Value = $"=D{row}*0.15";
            row++;
        }

        worksheet.AutoSizeColumn(0, true);

        using var ms = workbook.ToStream();
        return ms.ToArray();
    }
}

using IronXL;
using System.IO;
using ExportExcel.Models;

public class ExcelExportService
{
    public byte[] GenerateSalesReport(List<SalesData> salesData)
    {
        var workbook = WorkBook.Create(ExcelFileFormat.XLSX);
        workbook.Metadata.Author = "Sales Department";

        var worksheet = workbook.CreateWorkSheet("Monthly Sales");

        // Add column headers
        worksheet["A1"].Value = "Date";
        worksheet["B1"].Value = "Product";
        worksheet["C1"].Value = "Quantity";
        worksheet["D1"].Value = "Revenue";
        worksheet["E1"].Value = "Profit Margin";

        // Style the header row
        var headerRange = worksheet["A1:E1"];
        headerRange.Style.Font.Bold = true;
        headerRange.Style.BackgroundColor = "#4472C4";
        headerRange.Style.Font.Color = "#FFFFFF";

        // Populate data rows
        int row = 2;
        foreach (var sale in salesData)
        {
            worksheet[$"A{row}"].Value = sale.Date.ToString("yyyy-MM-dd");
            worksheet[$"B{row}"].Value = sale.Product ?? "Unknown";
            worksheet[$"C{row}"].Value = sale.Quantity;
            worksheet[$"D{row}"].Value = sale.Revenue;
            worksheet[$"E{row}"].Value = $"=D{row}*0.15";
            row++;
        }

        worksheet.AutoSizeColumn(0, true);

        using var ms = workbook.ToStream();
        return ms.ToArray();
    }
}

Registering the Service

Add the service to the DI container in Program.cs:

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddRazorPages();
builder.Services.AddServerSideBlazor();
builder.Services.AddScoped<ExcelExportService>();

var app = builder.Build();
app.MapBlazorHub();
app.MapFallbackToPage("/_Host");
app.Run();

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddRazorPages();
builder.Services.AddServerSideBlazor();
builder.Services.AddScoped<ExcelExportService>();

var app = builder.Build();
app.MapBlazorHub();
app.MapFallbackToPage("/_Host");
app.Run();

This service demonstrates several key IronXL capabilities. You can create new workbooks and worksheets with a single method call, apply styled headers, populate rows from any data source, and embed Excel formulas such as =D2*0.15. The AutoSizeColumn call ensures columns are wide enough to display their content correctly, regardless of data length. For further formatting options, see the cell styling guide.

Writing the Razor Component

Create a page at Pages/ExcelExportDashboard.razor:

@page "/excel-export"
@using ExportExcel.Models
@inject ExcelExportService ExcelService
@inject IJSRuntime JS

<h3>Excel Export Dashboard</h3>

<div class="export-section">
    <button class="btn btn-primary" @onclick="ExportSalesReport" disabled="@isExporting">
        @if (isExporting)
        {
            <span>Generating...</span>
        }
        else
        {
            <span>Export Sales Report</span>
        }
    </button>

    @if (!string.IsNullOrEmpty(errorMessage))
    {
        <div class="alert alert-danger mt-2">@errorMessage</div>
    }
</div>

@code {
    private bool isExporting = false;
    private string errorMessage = "";

    private async Task ExportSalesReport()
    {
        try
        {
            isExporting = true;
            errorMessage = "";

            var salesData = GetSalesData();
            var fileBytes = ExcelService.GenerateSalesReport(salesData);

            using var stream = new MemoryStream(fileBytes);
            using var streamRef = new DotNetStreamReference(stream);
            await JS.InvokeVoidAsync(
                "downloadFileFromStream",
                $"SalesReport_{DateTime.Now:yyyyMMdd}.xlsx",
                streamRef
            );
        }
        catch (Exception)
        {
            errorMessage = "Export failed. Please try again.";
        }
        finally
        {
            isExporting = false;
        }
    }

    private List<SalesData> GetSalesData()
    {
        return new List<SalesData>
        {
            new() { Date = DateTime.Now, Product = "Widget A", Quantity = 100, Revenue = 5000 },
            new() { Date = DateTime.Now.AddDays(-1), Product = "Widget B", Quantity = 75, Revenue = 3750 }
        };
    }
}

@page "/excel-export"
@using ExportExcel.Models
@inject ExcelExportService ExcelService
@inject IJSRuntime JS

<h3>Excel Export Dashboard</h3>

<div class="export-section">
    <button class="btn btn-primary" @onclick="ExportSalesReport" disabled="@isExporting">
        @if (isExporting)
        {
            <span>Generating...</span>
        }
        else
        {
            <span>Export Sales Report</span>
        }
    </button>

    @if (!string.IsNullOrEmpty(errorMessage))
    {
        <div class="alert alert-danger mt-2">@errorMessage</div>
    }
</div>

@code {
    private bool isExporting = false;
    private string errorMessage = "";

    private async Task ExportSalesReport()
    {
        try
        {
            isExporting = true;
            errorMessage = "";

            var salesData = GetSalesData();
            var fileBytes = ExcelService.GenerateSalesReport(salesData);

            using var stream = new MemoryStream(fileBytes);
            using var streamRef = new DotNetStreamReference(stream);
            await JS.InvokeVoidAsync(
                "downloadFileFromStream",
                $"SalesReport_{DateTime.Now:yyyyMMdd}.xlsx",
                streamRef
            );
        }
        catch (Exception)
        {
            errorMessage = "Export failed. Please try again.";
        }
        finally
        {
            isExporting = false;
        }
    }

    private List<SalesData> GetSalesData()
    {
        return new List<SalesData>
        {
            new() { Date = DateTime.Now, Product = "Widget A", Quantity = 100, Revenue = 5000 },
            new() { Date = DateTime.Now.AddDays(-1), Product = "Widget B", Quantity = 75, Revenue = 3750 }
        };
    }
}

What the Component Does

The isExporting flag disables the button during generation, preventing duplicate requests. The DotNetStreamReference wrapper handles efficient binary streaming from the .NET memory stream to the JavaScript function -- avoiding large base64 strings that would inflate payload size. Timestamped filenames such as SalesReport_20260228.xlsx keep downloads organized without additional configuration.

When you navigate to /excel-export in the browser, the dashboard page loads with an export button:

Clicking the button generates the spreadsheet and the browser automatically downloads the file:

Conditional Formatting for Inventory Reports

The following service highlights low-stock items in red -- a common requirement for warehouse or inventory management applications:

using IronXL;
using ExportExcel.Models;
using System.IO;

public class InventoryExportService
{
    public byte[] GenerateInventoryReport(List<InventoryItem> items)
    {
        var workbook = WorkBook.Create();
        var details = workbook.CreateWorkSheet("Inventory Details");

        // Column headers
        details["A1"].Value = "SKU";
        details["B1"].Value = "Name";
        details["C1"].Value = "Quantity";
        details["D1"].Value = "Reorder Level";
        details["E1"].Value = "Status";

        var headerRange = details["A1:E1"];
        headerRange.Style.Font.Bold = true;
        headerRange.Style.BackgroundColor = "#2E75B6";
        headerRange.Style.Font.Color = "#FFFFFF";

        for (int i = 0; i < items.Count; i++)
        {
            int row = i + 2;
            var item = items[i];

            details[$"A{row}"].Value = item.SKU;
            details[$"B{row}"].Value = item.Name;
            details[$"C{row}"].Value = item.Quantity;
            details[$"D{row}"].Value = item.ReorderLevel;
            details[$"E{row}"].Value = item.Quantity < item.ReorderLevel
                ? "Reorder Required"
                : "OK";

            if (item.Quantity < item.ReorderLevel)
            {
                // Highlight the entire row for low-stock items
                details[$"A{row}:E{row}"].Style.BackgroundColor = "#FFB6B6";
                details[$"C{row}"].Style.Font.Bold = true;
            }
        }

        details.AutoSizeColumn(0, true);
        details.AutoSizeColumn(1, true);

        using var stream = workbook.ToStream();
        return stream.ToArray();
    }
}

using IronXL;
using ExportExcel.Models;
using System.IO;

public class InventoryExportService
{
    public byte[] GenerateInventoryReport(List<InventoryItem> items)
    {
        var workbook = WorkBook.Create();
        var details = workbook.CreateWorkSheet("Inventory Details");

        // Column headers
        details["A1"].Value = "SKU";
        details["B1"].Value = "Name";
        details["C1"].Value = "Quantity";
        details["D1"].Value = "Reorder Level";
        details["E1"].Value = "Status";

        var headerRange = details["A1:E1"];
        headerRange.Style.Font.Bold = true;
        headerRange.Style.BackgroundColor = "#2E75B6";
        headerRange.Style.Font.Color = "#FFFFFF";

        for (int i = 0; i < items.Count; i++)
        {
            int row = i + 2;
            var item = items[i];

            details[$"A{row}"].Value = item.SKU;
            details[$"B{row}"].Value = item.Name;
            details[$"C{row}"].Value = item.Quantity;
            details[$"D{row}"].Value = item.ReorderLevel;
            details[$"E{row}"].Value = item.Quantity < item.ReorderLevel
                ? "Reorder Required"
                : "OK";

            if (item.Quantity < item.ReorderLevel)
            {
                // Highlight the entire row for low-stock items
                details[$"A{row}:E{row}"].Style.BackgroundColor = "#FFB6B6";
                details[$"C{row}"].Style.Font.Bold = true;
            }
        }

        details.AutoSizeColumn(0, true);
        details.AutoSizeColumn(1, true);

        using var stream = workbook.ToStream();
        return stream.ToArray();
    }
}

IronXL applies cell-level formatting based on data values at generation time. You can also apply conditional formatting rules declaratively, or manage multiple worksheets within the same workbook -- for example, one sheet for current stock and another for historical orders.

Adding Multiple Worksheets to a Single Export

Separating data into logical sheets improves readability without requiring separate downloads:

public byte[] GenerateMultiSheetReport(
    List<SalesData> sales,
    List<InventoryItem> inventory)
{
    var workbook = WorkBook.Create(ExcelFileFormat.XLSX);

    // Sheet 1 -- Sales summary
    var salesSheet = workbook.CreateWorkSheet("Sales");
    salesSheet["A1"].Value = "Date";
    salesSheet["B1"].Value = "Revenue";
    salesSheet["A1:B1"].Style.Font.Bold = true;

    for (int i = 0; i < sales.Count; i++)
    {
        salesSheet[$"A{i + 2}"].Value = sales[i].Date.ToString("yyyy-MM-dd");
        salesSheet[$"B{i + 2}"].Value = sales[i].Revenue;
    }

    // Sheet 2 -- Inventory snapshot
    var invSheet = workbook.CreateWorkSheet("Inventory");
    invSheet["A1"].Value = "SKU";
    invSheet["B1"].Value = "Name";
    invSheet["C1"].Value = "Quantity";
    invSheet["A1:C1"].Style.Font.Bold = true;

    for (int i = 0; i < inventory.Count; i++)
    {
        invSheet[$"A{i + 2}"].Value = inventory[i].SKU;
        invSheet[$"B{i + 2}"].Value = inventory[i].Name;
        invSheet[$"C{i + 2}"].Value = inventory[i].Quantity;
    }

    using var stream = workbook.ToStream();
    return stream.ToArray();
}

public byte[] GenerateMultiSheetReport(
    List<SalesData> sales,
    List<InventoryItem> inventory)
{
    var workbook = WorkBook.Create(ExcelFileFormat.XLSX);

    // Sheet 1 -- Sales summary
    var salesSheet = workbook.CreateWorkSheet("Sales");
    salesSheet["A1"].Value = "Date";
    salesSheet["B1"].Value = "Revenue";
    salesSheet["A1:B1"].Style.Font.Bold = true;

    for (int i = 0; i < sales.Count; i++)
    {
        salesSheet[$"A{i + 2}"].Value = sales[i].Date.ToString("yyyy-MM-dd");
        salesSheet[$"B{i + 2}"].Value = sales[i].Revenue;
    }

    // Sheet 2 -- Inventory snapshot
    var invSheet = workbook.CreateWorkSheet("Inventory");
    invSheet["A1"].Value = "SKU";
    invSheet["B1"].Value = "Name";
    invSheet["C1"].Value = "Quantity";
    invSheet["A1:C1"].Style.Font.Bold = true;

    for (int i = 0; i < inventory.Count; i++)
    {
        invSheet[$"A{i + 2}"].Value = inventory[i].SKU;
        invSheet[$"B{i + 2}"].Value = inventory[i].Name;
        invSheet[$"C{i + 2}"].Value = inventory[i].Quantity;
    }

    using var stream = workbook.ToStream();
    return stream.ToArray();
}

For a full API reference covering workbook properties, range operations, and chart support, visit the IronXL API documentation.

Error Handling in the Service Layer

Wrapping generation logic in the service (rather than the component) keeps error handling consistent across all callers. The recommended pattern is to let IronXL exceptions propagate, then wrap them in a domain-specific exception with context about which report failed:

Place a try/catch block around the workbook generation in GenerateSalesReport, catching Exception and rethrowing as InvalidOperationException("Failed to generate sales report", ex). In the Blazor component, catch the InvalidOperationException and display a user-friendly message without exposing internal details. Log the inner exception using ILogger<T> injected into the service constructor, so the development team can trace failures back to a specific workbook operation. Never surface raw exception messages to end users -- file paths, memory addresses, or stack traces can reveal server internals.

See error handling best practices in the official Microsoft documentation for guidance on structured error logging in Blazor. For more guidance on building testable services in .NET, the Microsoft dependency injection documentation explains how to register and resolve scoped services, which is exactly the pattern used here with ExcelExportService.

Performance Considerations for Large Datasets

For datasets exceeding a few thousand rows, consider these approaches:

IronXL's ToStream() method writes directly to an output stream without loading the entire file into a byte array first, which keeps memory usage lower for large workbooks. For additional performance guidance, see reading and writing large Excel files with IronXL.

Formulas, Named Ranges, and Number Formatting

You can embed any Excel formula using the same syntax you would type directly into a cell. IronXL evaluates formulas at read time, so consumers of the generated file see calculated results as soon as they open the spreadsheet. Named ranges make formulas more readable and maintainable over time:

// Aggregate formulas on a summary row
worksheet["E2"].Value = "=SUM(D2:D100)";
worksheet["F2"].Value = "=AVERAGE(C2:C100)";
worksheet["G2"].Value = "=COUNTIF(B2:B100,\"Widget A\")";

// Named ranges improve formula readability
worksheet["D2:D100"].Name = "RevenueColumn";
worksheet["E2"].Value = "=SUM(RevenueColumn)";

// Number and date formatting prevents type misinterpretation
worksheet["D2"].Value = 12345.67m;
worksheet["D2"].FormatString = "#,##0.00";
worksheet["A2"].Value = DateTime.Now;
worksheet["A2"].FormatString = "dd/MM/yyyy";

// Aggregate formulas on a summary row
worksheet["E2"].Value = "=SUM(D2:D100)";
worksheet["F2"].Value = "=AVERAGE(C2:C100)";
worksheet["G2"].Value = "=COUNTIF(B2:B100,\"Widget A\")";

// Named ranges improve formula readability
worksheet["D2:D100"].Name = "RevenueColumn";
worksheet["E2"].Value = "=SUM(RevenueColumn)";

// Number and date formatting prevents type misinterpretation
worksheet["D2"].Value = 12345.67m;
worksheet["D2"].FormatString = "#,##0.00";
worksheet["A2"].Value = DateTime.Now;
worksheet["A2"].FormatString = "dd/MM/yyyy";

To define named ranges and set the number format explicitly, IronXL exposes both as properties on the range object. This prevents Excel from treating currency values as plain text -- a common issue when exporting financial data from databases that store values as strings.

Supported Excel File Formats

IronXL can read and write multiple Excel formats including .xlsx, .xls, .csv, and .tsv. The format is determined at save time, so the same service class can support both Excel and CSV exports with a small parameter change:

// Export as CSV for systems that consume flat files
workbook.SaveAs("report.csv");

// Or stream as CSV for download
using var ms = workbook.ToStream(ExcelFileFormat.CSV);

// Export as CSV for systems that consume flat files
workbook.SaveAs("report.csv");

// Or stream as CSV for download
using var ms = workbook.ToStream(ExcelFileFormat.CSV);

This flexibility matters in integrations where downstream systems -- such as ERP platforms or data warehouses -- expect a specific file format. For a full feature comparison between IronXL and other Excel libraries, visit the IronXL features page.

Microsoft provides a good reference for understanding OOXML file formats if you need to understand the internal structure of .xlsx files when debugging unexpected output. The NuGet package for IronXL is also listed on NuGet.org with full version history and compatibility notes.