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How to create .NET PDF API Using IronPDF

Chipego
Chipego Kalinda
Published:

When working with modern applications, .NET developers like yourself may find themselves needing to build a centralized PDF generation service. Whether you're generating invoices, reports, certificates, or contracts, having a dedicated .NET PDF API can be beneficial for efficiently managing PDF files. So how can it improve your PDF generation tasks? It does this through providing consistency, maintainability, and scalability across your desktop and web applications. Never before has it been easier to manage document content, PDF pages, and PDF form fields.

In this tutorial, you'll learn how to build a production-ready PDF API using ASP.NET Core and IronPDF, a powerful .NET PDF library. We'll create RESTful endpoints that can generate PDFs from HTML, merge documents, add watermarks, and handle various real-world PDF generation scenarios in your Web API.

Why Build a Dedicated PDF API?

Before diving into the code, let's understand why creating a dedicated PDF API makes sense:

  • Centralized Logic: All PDF generation logic lives in one place, making maintenance and updates easier
  • Microservice Architecture: Perfect for service-oriented architectures where different applications need PDF capabilities
  • Performance Optimization: Easier to scale and optimize a dedicated service for large PDF files, multiple pages, and dynamic data.
  • Language Agnostic: Any client application can consume the API regardless of programming language
  • Consistent Output: Ensures all PDF documents across your organization maintain consistent document layout, paragraph formatting, and PDF content.

Ready to start building? Download IronPDF's free trial and follow along with this tutorial to programmatically create PDF files in your .NET Framework projects.

IronPDF: The Complete .NET PDF Library

IronPDF stands out as the premier PDF library for .NET developers, offering a comprehensive set of features that make PDF generation in Web API projects straightforward and reliable. It's built on a Chrome rendering engine, which ensures pixel-perfect HTML-to-PDF conversions, often in just a few lines of code. It does all of this while maintaining all styling, JavaScript execution, and responsive layouts.

Key capabilities that make IronPDF ideal for .NET PDF API development:

  • Chrome-Based Rendering: Leverages Google Chrome's rendering engine for converting PDF documents from HTML content accurately, with full support for embedded images and other web assets
  • Rich Feature Set: Supports the editing of new and existing documents with digital signatures, PDF forms, annotations, encryption, compression, and more
  • Create Secure PDF Documents: Manage sensitive PDF content with encryption, digital signatures, and document protection.
  • Multiple Input Formats: Use HTML, URLs, images, and Office documents to create PDF documents
  • Advanced Manipulation: Merge PDF pages, split documents, apply watermarks, create interactive PDF forms, and manipulate PDF files programmatically.
  • Cross-Platform Support: Works on Windows, Linux, macOS, Docker, and cloud platforms
  • Performance Optimized: Async operations, efficient memory management, and fast rendering

How to Set Up Your PDF Document API Project?

Let's start by creating a new ASP.NET Core Web API project and installing the necessary packages.

Prerequisites

  • .NET 6.0 SDK or later
  • Visual Studio 2022 or Visual Studio Code
  • Postman or a similar API testing tool for testing your PDF REST API

Creating the Project

First, let's create the project within which we will build our PDF generation tool.

dotnet new webapi -n PdfApiService
cd PdfApiService

Installing IronPDF

The next step is to add IronPDF to your project via NuGet:

dotnet add package IronPdf

Or, using the NuGet Package Manager Console in Visual Studio:

Install-Package IronPdf

Project Structure

An essential aspect of C# development is maintaining a clean and well-structured project folder. For example:

How to Create Your First PDF Endpoint?

Let's build a simple endpoint that converts HTML to PDF format. First, create the service interface and implementation:

Creating the PDF Service

First, we will add the following to our IPdfService.cs file:

public interface IPdfService
{
    byte[] GeneratePdfFromHtml(string htmlContent);
    byte[] GeneratePdfFromUrl(string url);
}
public interface IPdfService
{
    byte[] GeneratePdfFromHtml(string htmlContent);
    byte[] GeneratePdfFromUrl(string url);
}
IRON VB CONVERTER ERROR developers@ironsoftware.com
$vbLabelText   $csharpLabel

In the PdfService.cs file, we will add this:

using IronPdf;
public class PdfService : IPdfService
{
    private readonly ChromePdfRenderer _renderer;
    public PdfService()
    {
        _renderer = new ChromePdfRenderer();
        // Configure rendering options for optimal PDF generation in .NET
        _renderer.RenderingOptions.MarginTop = 20;
        _renderer.RenderingOptions.MarginBottom = 20;
        _renderer.RenderingOptions.PrintHtmlBackgrounds = true;
    }
    public byte[] GeneratePdfFromHtml(string htmlContent)
    {
        // Generate PDF from HTML using the .NET PDF API
        var pdf = _renderer.RenderHtmlAsPdf(htmlContent);
        return pdf.BinaryData;
    }
    public byte[] GeneratePdfFromUrl(string url)
    {
        // Convert URL to PDF in the REST API
        var pdf = _renderer.RenderUrlAsPdf(url);
        return pdf.BinaryData;
    }
}
using IronPdf;
public class PdfService : IPdfService
{
    private readonly ChromePdfRenderer _renderer;
    public PdfService()
    {
        _renderer = new ChromePdfRenderer();
        // Configure rendering options for optimal PDF generation in .NET
        _renderer.RenderingOptions.MarginTop = 20;
        _renderer.RenderingOptions.MarginBottom = 20;
        _renderer.RenderingOptions.PrintHtmlBackgrounds = true;
    }
    public byte[] GeneratePdfFromHtml(string htmlContent)
    {
        // Generate PDF from HTML using the .NET PDF API
        var pdf = _renderer.RenderHtmlAsPdf(htmlContent);
        return pdf.BinaryData;
    }
    public byte[] GeneratePdfFromUrl(string url)
    {
        // Convert URL to PDF in the REST API
        var pdf = _renderer.RenderUrlAsPdf(url);
        return pdf.BinaryData;
    }
}
IRON VB CONVERTER ERROR developers@ironsoftware.com
$vbLabelText   $csharpLabel

The PdfService handles the core process of converting HTML into PDF. Utilizing IronPDF’s ChromePdfRenderer, this class is set up with sensible defaults like page margins and background rendering to produce a polished final document.

When the controller passes in raw HTML, the service uses IronPDF to render it into a professional-quality PDF and returns the result as byte data, ready to download. Additionally, it can also handle entire web pages by converting a URL directly into a PDF.

Creating the Controller

Now it's time to create the controller for our API. This will provide an API endpoint capable of generating PDF files from HTML. It will then be able to download and save PDF documents to your system for further use or sharing.

// Controllers/PdfController.cs
using Microsoft.AspNetCore.Mvc;
[ApiController]
[Route("api/[controller]")]
public class PdfController : ControllerBase
{
    private readonly IPdfService _pdfService;
    public PdfController(IPdfService pdfService)
    {
        _pdfService = pdfService;
    }
    [HttpPost("html-to-pdf")]
    public IActionResult ConvertHtmlToPdf([FromBody] HtmlRequest request)
    {
        try
        {
            var pdfBytes = _pdfService.GeneratePdfFromHtml(request.HtmlContent);
            // Return as downloadable file
            return File(pdfBytes, "application/pdf", "document.pdf");
        }
        catch (Exception ex)
        {
            return BadRequest($"Error generating PDF: {ex.Message}");
        }
    }
}
// Controllers/PdfController.cs
using Microsoft.AspNetCore.Mvc;
[ApiController]
[Route("api/[controller]")]
public class PdfController : ControllerBase
{
    private readonly IPdfService _pdfService;
    public PdfController(IPdfService pdfService)
    {
        _pdfService = pdfService;
    }
    [HttpPost("html-to-pdf")]
    public IActionResult ConvertHtmlToPdf([FromBody] HtmlRequest request)
    {
        try
        {
            var pdfBytes = _pdfService.GeneratePdfFromHtml(request.HtmlContent);
            // Return as downloadable file
            return File(pdfBytes, "application/pdf", "document.pdf");
        }
        catch (Exception ex)
        {
            return BadRequest($"Error generating PDF: {ex.Message}");
        }
    }
}
IRON VB CONVERTER ERROR developers@ironsoftware.com
$vbLabelText   $csharpLabel

Then, in the HtmlRequest.cs file, we will add this:

// Models/HtmlRequest.cs
public class HtmlRequest
{
    public string HtmlContent { get; set; }
    public string FileName { get; set; } = "document.pdf";
}
// Models/HtmlRequest.cs
public class HtmlRequest
{
    public string HtmlContent { get; set; }
    public string FileName { get; set; } = "document.pdf";
}
IRON VB CONVERTER ERROR developers@ironsoftware.com
$vbLabelText   $csharpLabel

In the first file, we set up a straightforward API endpoint that turns HTML into a downloadable PDF. When someone sends HTML content to the api/pdf/html-to-pdf route with a simple POST request, the PdfController passes the job of converting it into a PDF to a dedicated service.

Once the PDF is created, the controller hands it back to the user as a ready-to-download file. The request itself is structured using the HtmlRequest model, which carries both the raw HTML and an optional file name for the final document. In short, this setup makes it easy for clients to send HTML and instantly receive a polished PDF in return.

Registering Services

Update your Program.cs to register the PDF service:

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddControllers();
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();
// Register PDF service
builder.Services.AddSingleton<IPdfService, PdfService>();
var app = builder.Build();
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}
app.UseHttpsRedirection();
app.MapControllers();
app.Run();
var builder = WebApplication.CreateBuilder(args);
builder.Services.AddControllers();
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();
// Register PDF service
builder.Services.AddSingleton<IPdfService, PdfService>();
var app = builder.Build();
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}
app.UseHttpsRedirection();
app.MapControllers();
app.Run();
IRON VB CONVERTER ERROR developers@ironsoftware.com
$vbLabelText   $csharpLabel

How to Handle Different Response Types?

Your API should support different ways of returning PDFs based on client needs:

[HttpPost("generate")]
 public IActionResult GeneratePdf([FromBody] PdfRequest request)
 {
     var pdfBytes = _pdfService.GeneratePdfFromHtml(request.HtmlContent);
     switch (request.ResponseType?.ToLower())
     {
         case "base64":
             return Ok(new
             {
                 data = Convert.ToBase64String(pdfBytes),
                 filename = request.FileName
             });
         case "inline":
             return File(pdfBytes, "application/pdf");
         default: // download
             return File(pdfBytes, "application/pdf", request.FileName);
     }
 }
[HttpPost("generate")]
 public IActionResult GeneratePdf([FromBody] PdfRequest request)
 {
     var pdfBytes = _pdfService.GeneratePdfFromHtml(request.HtmlContent);
     switch (request.ResponseType?.ToLower())
     {
         case "base64":
             return Ok(new
             {
                 data = Convert.ToBase64String(pdfBytes),
                 filename = request.FileName
             });
         case "inline":
             return File(pdfBytes, "application/pdf");
         default: // download
             return File(pdfBytes, "application/pdf", request.FileName);
     }
 }
IRON VB CONVERTER ERROR developers@ironsoftware.com
$vbLabelText   $csharpLabel

Here, we have added a more flexible PDF generation endpoint to the controller. Instead of always forcing a file download, the GeneratePdf method lets the client choose how they want the result returned. This option offers flexibility, allowing PDFs to be displayed in various formats: as a downloadable file, directly in the browser, or encoded as a Base64 string for easy use in APIs.

The request is defined by the PdfRequest model, which builds on the earlier HtmlRequest and adds a ResponseType option. In short, this gives users more control over how they receive their PDFs, making the API more versatile and user-friendly.

Now, when we run our program, we'll see this output on Swagger.

How to create .NET PDF API Using IronPDF: Figure 4 - Swagger UI

How to Implement Common PDF Operations?

Let's expand our service to handle various PDF generation scenarios:

URL to PDF Conversion

[HttpPost("url-to-pdf")]
public async Task<IActionResult> ConvertUrlToPdf([FromBody] UrlRequest request)
{
    try
    {
        var pdfBytes = await Task.Run(() => 
            _pdfService.GeneratePdfFromUrl(request.Url));
        return File(pdfBytes, "application/pdf", 
            $"{request.FileName ?? "website"}.pdf");
    }
    catch (Exception ex)
    {
        return BadRequest($"Failed to convert URL: {ex.Message}");
    }
}
public class UrlRequest
{
    public string Url { get; set; }
    public string FileName { get; set; }
}
[HttpPost("url-to-pdf")]
public async Task<IActionResult> ConvertUrlToPdf([FromBody] UrlRequest request)
{
    try
    {
        var pdfBytes = await Task.Run(() => 
            _pdfService.GeneratePdfFromUrl(request.Url));
        return File(pdfBytes, "application/pdf", 
            $"{request.FileName ?? "website"}.pdf");
    }
    catch (Exception ex)
    {
        return BadRequest($"Failed to convert URL: {ex.Message}");
    }
}
public class UrlRequest
{
    public string Url { get; set; }
    public string FileName { get; set; }
}
IRON VB CONVERTER ERROR developers@ironsoftware.com
$vbLabelText   $csharpLabel

This endpoint lets clients send a URL and get back a ready-to-download PDF of that webpage. When a POST /api/pdf/url-to-pdf request comes in, the controller uses _pdfService to convert the given URL into PDF bytes in the background, then returns them as a file download. If something goes wrong during conversion, it gracefully responds with a clear error message.

Let's try using the URL "https://www.apple.com/nz" and test the POST request. Below is the output we obtained.

Output

How to create .NET PDF API Using IronPDF: Figure 5 - URL PDF output

Adding Custom Watermarks

public byte[] AddWatermarkFromFile(string filePath, string watermarkText)
{
    // Load PDF directly from file
    var pdf = PdfDocument.FromFile(filePath);
    pdf.ApplyWatermark(
        $"<h1 style='color:red;font-size:72px;'>{watermarkText}</h1>",
        75,
        IronPdf.Editing.VerticalAlignment.Middle,
        IronPdf.Editing.HorizontalAlignment.Center
    );
    return pdf.BinaryData;
}
public byte[] AddWatermarkFromFile(string filePath, string watermarkText)
{
    // Load PDF directly from file
    var pdf = PdfDocument.FromFile(filePath);
    pdf.ApplyWatermark(
        $"<h1 style='color:red;font-size:72px;'>{watermarkText}</h1>",
        75,
        IronPdf.Editing.VerticalAlignment.Middle,
        IronPdf.Editing.HorizontalAlignment.Center
    );
    return pdf.BinaryData;
}
IRON VB CONVERTER ERROR developers@ironsoftware.com
$vbLabelText   $csharpLabel

Here, we are just manually loading a local file for testing purposes. However, you can adjust this so your PDF API generates a PDF document, and then apply a custom watermark to it with ease.

Watermark Output

How to create .NET PDF API Using IronPDF: Figure 6 - Watermark output from code example above

How to Add Dynamic Data with Templates

For real-world applications, you'll often need to generate PDFs from templates with dynamic data:

[HttpPost("from-template")]
public IActionResult GenerateFromTemplate([FromBody] TemplateRequest request)
{
    // Simple template replacement
    var html = request.Template;
    foreach (var item in request.Data)
    {
        html = html.Replace($"{{{{{item.Key}}}}}", item.Value);
    }
    var pdfBytes = _pdfService.GeneratePdfFromHtml(html);
    return File(pdfBytes, "application/pdf", request.FileName);
}
public class TemplateRequest
{
    public string Template { get; set; }
    public Dictionary<string, string> Data { get; set; }
    public string FileName { get; set; } = "document.pdf";
}
[HttpPost("from-template")]
public IActionResult GenerateFromTemplate([FromBody] TemplateRequest request)
{
    // Simple template replacement
    var html = request.Template;
    foreach (var item in request.Data)
    {
        html = html.Replace($"{{{{{item.Key}}}}}", item.Value);
    }
    var pdfBytes = _pdfService.GeneratePdfFromHtml(html);
    return File(pdfBytes, "application/pdf", request.FileName);
}
public class TemplateRequest
{
    public string Template { get; set; }
    public Dictionary<string, string> Data { get; set; }
    public string FileName { get; set; } = "document.pdf";
}
IRON VB CONVERTER ERROR developers@ironsoftware.com
$vbLabelText   $csharpLabel

For more advanced template scenarios with Razor, Handlebars, or other engines, check out IronPDF's HTML to PDF documentation. You can also explore CSHTML to PDF conversion for MVC applications and Razor to PDF for Blazor applications.

How to Optimize Performance?

When building a production PDF API, performance is crucial. Here are key optimization strategies:

Async Operations

When building projects that involve the use of I/O operations, it is wise to use asynchronous coding. This is especially helpful if your PDF content comes from external resources like:

  • Downloading HTML pages (RenderUrlAsPdf)
  • Fetching images, CSS, or fonts over HTTP
  • Reading/writing files to disk or cloud storage

These operations can then block a thread, but using async prevents your API thread from waiting idle.

Example:

public async Task<byte[]> GeneratePdfFromHtmlAsync(string htmlContent)
{
    return await Task.Run(() => 
    {
        var pdf = _renderer.RenderHtmlAsPdf(htmlContent);
        return pdf.BinaryData;
    });
}
public async Task<byte[]> GeneratePdfFromHtmlAsync(string htmlContent)
{
    return await Task.Run(() => 
    {
        var pdf = _renderer.RenderHtmlAsPdf(htmlContent);
        return pdf.BinaryData;
    });
}
IRON VB CONVERTER ERROR developers@ironsoftware.com
$vbLabelText   $csharpLabel

Rendering Options

Configure IronPDF for optimal performance:

_renderer.RenderingOptions.EnableJavaScript = false; // If JS not needed
_renderer.RenderingOptions.CssMediaType = PdfCssMediaType.Print;
_renderer.RenderingOptions.RenderDelay = 0; // Remove if no JS
_renderer.RenderingOptions.Timeout = 30; // Set reasonable timeout
_renderer.RenderingOptions.EnableJavaScript = false; // If JS not needed
_renderer.RenderingOptions.CssMediaType = PdfCssMediaType.Print;
_renderer.RenderingOptions.RenderDelay = 0; // Remove if no JS
_renderer.RenderingOptions.Timeout = 30; // Set reasonable timeout
IRON VB CONVERTER ERROR developers@ironsoftware.com
$vbLabelText   $csharpLabel

How to Secure Your PDF API?

Security is essential for any production API. Here's a simple API key authentication approach:

// Middleware/ApiKeyMiddleware.cs
public class ApiKeyMiddleware
{
    private readonly RequestDelegate _next;
    private const string ApiKeyHeader = "X-API-Key";
    public ApiKeyMiddleware(RequestDelegate next)
    {
        _next = next;
    }
    public async Task InvokeAsync(HttpContext context)
    {
        if (!context.Request.Headers.TryGetValue(ApiKeyHeader, out var apiKey))
        {
            context.Response.StatusCode = 401;
            await context.Response.WriteAsync("API Key required");
            return;
        }
        // Validate API key (in production, check against database)
        var validApiKey = context.RequestServices
            .GetRequiredService<IConfiguration>()["ApiKey"];
        if (apiKey != validApiKey)
        {
            context.Response.StatusCode = 403;
            await context.Response.WriteAsync("Invalid API Key");
            return;
        }
        await _next(context);
    }
}
// In Program.cs
app.UseMiddleware<ApiKeyMiddleware>();
// Middleware/ApiKeyMiddleware.cs
public class ApiKeyMiddleware
{
    private readonly RequestDelegate _next;
    private const string ApiKeyHeader = "X-API-Key";
    public ApiKeyMiddleware(RequestDelegate next)
    {
        _next = next;
    }
    public async Task InvokeAsync(HttpContext context)
    {
        if (!context.Request.Headers.TryGetValue(ApiKeyHeader, out var apiKey))
        {
            context.Response.StatusCode = 401;
            await context.Response.WriteAsync("API Key required");
            return;
        }
        // Validate API key (in production, check against database)
        var validApiKey = context.RequestServices
            .GetRequiredService<IConfiguration>()["ApiKey"];
        if (apiKey != validApiKey)
        {
            context.Response.StatusCode = 403;
            await context.Response.WriteAsync("Invalid API Key");
            return;
        }
        await _next(context);
    }
}
// In Program.cs
app.UseMiddleware<ApiKeyMiddleware>();
IRON VB CONVERTER ERROR developers@ironsoftware.com
$vbLabelText   $csharpLabel

For more advanced authentication scenarios, consider:

Real-World Example: Invoice Generation API

Let's build a practical invoice generation endpoint that demonstrates a complete implementation. This example shows how a production .NET PDF API can generate professional invoices with dynamic data.

Get stated with IronPDF now.
green arrow pointer

First, we'll create a new file in our Models folder. Here, I've called mine Invoice.cs. Then, add the following code to your new file.

public class Invoice
{
    public string InvoiceNumber { get; set; }
    public DateTime Date { get; set; }
    public string CustomerName { get; set; }
    public string CustomerAddress { get; set; }
    public List<InvoiceItem> Items { get; set; }
    public decimal Tax { get; set; }
}
public class InvoiceItem
{
    public string Description { get; set; }
    public int Quantity { get; set; }
    public decimal UnitPrice { get; set; }
    public decimal Total => Quantity * UnitPrice;
}
public class Invoice
{
    public string InvoiceNumber { get; set; }
    public DateTime Date { get; set; }
    public string CustomerName { get; set; }
    public string CustomerAddress { get; set; }
    public List<InvoiceItem> Items { get; set; }
    public decimal Tax { get; set; }
}
public class InvoiceItem
{
    public string Description { get; set; }
    public int Quantity { get; set; }
    public decimal UnitPrice { get; set; }
    public decimal Total => Quantity * UnitPrice;
}
IRON VB CONVERTER ERROR developers@ironsoftware.com
$vbLabelText   $csharpLabel

Then, we'll need to create a new service file for our invoice generator. In your Services folder, add the following code. For mine, I made a new file called InvoiceService.cs. This code will handle the styling and layout of our Invoice PDF file.

public class InvoiceService
{
    private readonly ChromePdfRenderer _renderer;
    public InvoiceService()
    {
        _renderer = new ChromePdfRenderer();
        _renderer.RenderingOptions.MarginTop = 10;
        _renderer.RenderingOptions.MarginBottom = 10;
        _renderer.RenderingOptions.PrintHtmlBackgrounds = true;
    }
    public byte[] GenerateInvoice(Invoice invoice)
{
    var html = BuildInvoiceHtml(invoice);
    // Add footer with page numbers
    _renderer.RenderingOptions.HtmlFooter = new HtmlHeaderFooter
    {
        MaxHeight = 15,
        HtmlFragment = "<center><i>{page} of {total-pages}</i></center>",
        DrawDividerLine = true
    };
    var pdf = _renderer.RenderHtmlAsPdf(html);
    return pdf.BinaryData;
}
    private string BuildInvoiceHtml(Invoice invoice)
    {
        var subtotal = invoice.Items.Sum(i => i.Total);
        var taxAmount = subtotal * (invoice.Tax / 100);
        var total = subtotal + taxAmount;
        var itemsHtml = string.Join("", invoice.Items.Select(item => 
            $@"<tr>
                <td>{item.Description}</td>
                <td class='text-center'>{item.Quantity}</td>
                <td class='text-right'>${item.UnitPrice:F2}</td>
                <td class='text-right'>${item.Total:F2}</td>
            </tr>"));
        return $@"
        <!DOCTYPE html>
        <html>
        <head>
            <style>
                body {{ font-family: Arial, sans-serif; }}
                .invoice-header {{ 
                    background-color: #f8f9fa; 
                    padding: 20px; 
                    margin-bottom: 20px; 
                }}
                table {{ 
                    width: 100%; 
                    border-collapse: collapse; 
                }}
                th, td {{ 
                    padding: 10px; 
                    border-bottom: 1px solid #ddd; 
                }}
                th {{ 
                    background-color: #007bff; 
                    color: white; 
                }}
                .text-right {{ text-align: right; }}
                .text-center {{ text-align: center; }}
                .total-section {{ 
                    margin-top: 20px; 
                    text-align: right; 
                }}
            </style>
        </head>
        <body>
            <div class='invoice-header'>
                <h1>Invoice #{invoice.InvoiceNumber}</h1>
                <p>Date: {invoice.Date:yyyy-MM-dd}</p>
            </div>   
            <div>
                <h3>Bill To:</h3>
                <p>{invoice.CustomerName}<br/>{invoice.CustomerAddress}</p>
            </div>    
            <table>
                <thead>
                    <tr>
                        <th>Description</th>
                        <th>Quantity</th>
                        <th>Unit Price</th>
                        <th>Total</th>
                    </tr>
                </thead>
                <tbody>
                    {itemsHtml}
                </tbody>
            </table>
            <div class='total-section'>
                <p>Subtotal: ${subtotal:F2}</p>
                <p>Tax ({invoice.Tax}%): ${taxAmount:F2}</p>
                <h3>Total: ${total:F2}</h3>
            </div>
        </body>
        </html>";
    }
}
public class InvoiceService
{
    private readonly ChromePdfRenderer _renderer;
    public InvoiceService()
    {
        _renderer = new ChromePdfRenderer();
        _renderer.RenderingOptions.MarginTop = 10;
        _renderer.RenderingOptions.MarginBottom = 10;
        _renderer.RenderingOptions.PrintHtmlBackgrounds = true;
    }
    public byte[] GenerateInvoice(Invoice invoice)
{
    var html = BuildInvoiceHtml(invoice);
    // Add footer with page numbers
    _renderer.RenderingOptions.HtmlFooter = new HtmlHeaderFooter
    {
        MaxHeight = 15,
        HtmlFragment = "<center><i>{page} of {total-pages}</i></center>",
        DrawDividerLine = true
    };
    var pdf = _renderer.RenderHtmlAsPdf(html);
    return pdf.BinaryData;
}
    private string BuildInvoiceHtml(Invoice invoice)
    {
        var subtotal = invoice.Items.Sum(i => i.Total);
        var taxAmount = subtotal * (invoice.Tax / 100);
        var total = subtotal + taxAmount;
        var itemsHtml = string.Join("", invoice.Items.Select(item => 
            $@"<tr>
                <td>{item.Description}</td>
                <td class='text-center'>{item.Quantity}</td>
                <td class='text-right'>${item.UnitPrice:F2}</td>
                <td class='text-right'>${item.Total:F2}</td>
            </tr>"));
        return $@"
        <!DOCTYPE html>
        <html>
        <head>
            <style>
                body {{ font-family: Arial, sans-serif; }}
                .invoice-header {{ 
                    background-color: #f8f9fa; 
                    padding: 20px; 
                    margin-bottom: 20px; 
                }}
                table {{ 
                    width: 100%; 
                    border-collapse: collapse; 
                }}
                th, td {{ 
                    padding: 10px; 
                    border-bottom: 1px solid #ddd; 
                }}
                th {{ 
                    background-color: #007bff; 
                    color: white; 
                }}
                .text-right {{ text-align: right; }}
                .text-center {{ text-align: center; }}
                .total-section {{ 
                    margin-top: 20px; 
                    text-align: right; 
                }}
            </style>
        </head>
        <body>
            <div class='invoice-header'>
                <h1>Invoice #{invoice.InvoiceNumber}</h1>
                <p>Date: {invoice.Date:yyyy-MM-dd}</p>
            </div>   
            <div>
                <h3>Bill To:</h3>
                <p>{invoice.CustomerName}<br/>{invoice.CustomerAddress}</p>
            </div>    
            <table>
                <thead>
                    <tr>
                        <th>Description</th>
                        <th>Quantity</th>
                        <th>Unit Price</th>
                        <th>Total</th>
                    </tr>
                </thead>
                <tbody>
                    {itemsHtml}
                </tbody>
            </table>
            <div class='total-section'>
                <p>Subtotal: ${subtotal:F2}</p>
                <p>Tax ({invoice.Tax}%): ${taxAmount:F2}</p>
                <h3>Total: ${total:F2}</h3>
            </div>
        </body>
        </html>";
    }
}
IRON VB CONVERTER ERROR developers@ironsoftware.com
$vbLabelText   $csharpLabel

Finally, you will need to create a new Controller in order to access and create a new Invoice using the API.

[ApiController]
[Route("api/[controller]")]
public class InvoiceController : ControllerBase
{
    private readonly InvoiceService _invoiceService;
    public InvoiceController(InvoiceService invoiceService)
    {
        _invoiceService = invoiceService;
    }
    [HttpPost("generate")]
    public IActionResult GenerateInvoice([FromBody] Invoice invoice)
    {
        try
        {
            var pdfBytes = _invoiceService.GenerateInvoice(invoice);
            var fileName = $"Invoice_{invoice.InvoiceNumber}.pdf";
            return File(pdfBytes, "application/pdf", fileName);
        }
        catch (Exception ex)
        {
            return StatusCode(500, $"Error generating invoice: {ex.Message}");
        }
    }
}
[ApiController]
[Route("api/[controller]")]
public class InvoiceController : ControllerBase
{
    private readonly InvoiceService _invoiceService;
    public InvoiceController(InvoiceService invoiceService)
    {
        _invoiceService = invoiceService;
    }
    [HttpPost("generate")]
    public IActionResult GenerateInvoice([FromBody] Invoice invoice)
    {
        try
        {
            var pdfBytes = _invoiceService.GenerateInvoice(invoice);
            var fileName = $"Invoice_{invoice.InvoiceNumber}.pdf";
            return File(pdfBytes, "application/pdf", fileName);
        }
        catch (Exception ex)
        {
            return StatusCode(500, $"Error generating invoice: {ex.Message}");
        }
    }
}
IRON VB CONVERTER ERROR developers@ironsoftware.com
$vbLabelText   $csharpLabel

Invoice Output

How to create .NET PDF API Using IronPDF: Figure 7 - PDF Invoice output

Container Deployment Considerations

While this tutorial focuses on local development, here's a brief overview of containerizing your PDF API:

Basic Dockerfile

FROM mcr.microsoft.com/dotnet/aspnet:6.0 AS base
WORKDIR /app
EXPOSE 80
FROM mcr.microsoft.com/dotnet/sdk:6.0 AS build
WORKDIR /src
COPY ["PdfApiService.csproj", "."]
RUN dotnet restore
COPY . .
RUN dotnet build -c Release -o /app/build
FROM build AS publish
RUN dotnet publish -c Release -o /app/publish
FROM base AS final
WORKDIR /app
COPY --from=publish /app/publish .
# IronPDF requires additional dependencies on Linux
RUN apt-get update && apt-get install -y \
    libgdiplus \
    libc6-dev \
    libx11-dev \
    && rm -rf /var/lib/apt/lists/*     
ENTRYPOINT ["dotnet", "PdfApiService.dll"]
FROM mcr.microsoft.com/dotnet/aspnet:6.0 AS base
WORKDIR /app
EXPOSE 80
FROM mcr.microsoft.com/dotnet/sdk:6.0 AS build
WORKDIR /src
COPY ["PdfApiService.csproj", "."]
RUN dotnet restore
COPY . .
RUN dotnet build -c Release -o /app/build
FROM build AS publish
RUN dotnet publish -c Release -o /app/publish
FROM base AS final
WORKDIR /app
COPY --from=publish /app/publish .
# IronPDF requires additional dependencies on Linux
RUN apt-get update && apt-get install -y \
    libgdiplus \
    libc6-dev \
    libx11-dev \
    && rm -rf /var/lib/apt/lists/*     
ENTRYPOINT ["dotnet", "PdfApiService.dll"]
IRON VB CONVERTER ERROR developers@ironsoftware.com
$vbLabelText   $csharpLabel

For detailed deployment guides for your .NET PDF API, see:

Error Handling Best Practices

For a more fault-tolerant program, the best practices are to implement a global error handler for consistent error responses, such as below:

// Middleware/ErrorHandlingMiddleware.cs
public class ErrorHandlingMiddleware
{
    private readonly RequestDelegate _next;
    public ErrorHandlingMiddleware(RequestDelegate next)
    {
        _next = next;
    }
    public async Task InvokeAsync(HttpContext context)
    {
        try
        {
            await _next(context);
        }
        catch (Exception ex)
        {
            await HandleExceptionAsync(context, ex);
        }
    }
    private static async Task HandleExceptionAsync(HttpContext context, Exception ex)
    {
        context.Response.ContentType = "application/json";
        context.Response.StatusCode = 500;
        var response = new
        {
            error = "An error occurred processing your request",
            message = ex.Message
        };
        await context.Response.WriteAsync(JsonSerializer.Serialize(response));
    }
}
// Middleware/ErrorHandlingMiddleware.cs
public class ErrorHandlingMiddleware
{
    private readonly RequestDelegate _next;
    public ErrorHandlingMiddleware(RequestDelegate next)
    {
        _next = next;
    }
    public async Task InvokeAsync(HttpContext context)
    {
        try
        {
            await _next(context);
        }
        catch (Exception ex)
        {
            await HandleExceptionAsync(context, ex);
        }
    }
    private static async Task HandleExceptionAsync(HttpContext context, Exception ex)
    {
        context.Response.ContentType = "application/json";
        context.Response.StatusCode = 500;
        var response = new
        {
            error = "An error occurred processing your request",
            message = ex.Message
        };
        await context.Response.WriteAsync(JsonSerializer.Serialize(response));
    }
}
IRON VB CONVERTER ERROR developers@ironsoftware.com
$vbLabelText   $csharpLabel

For specific IronPDF troubleshooting scenarios, refer to the IronPDF troubleshooting guide.

Conclusion

You've now built a robust .NET PDF API using ASP.NET Core and IronPDF that can handle various document generation scenarios. This REST API provides a solid foundation for centralized PDF operations in your applications.

Key takeaways:

  • IronPDF makes PDF generation in Web API projects straightforward with its Chrome-based rendering
  • You can easily adjust your Web API to edit existing PDF documents with IronPDF's advanced editing tools
  • RESTful design principles ensure your PDF API is intuitive and maintainable
  • Proper error handling and security measures are essential for production
  • Performance optimization through async operations and caching improves scalability
  • You will have support for desktop and web applications with scalable document solutions

IronPDF allows developers to create PDF documents, save PDF files, and convert HTML efficiently, making it the essential PDF document API for modern .NET Framework applications.

Next Steps

Ready to implement IronPDF in your production .NET PDF API? Here are your next actions:

  1. Start your free trial - Test IronPDF with full functionality in your development environment
  2. Explore advanced features - Check out digital signatures, PDF forms, and other advanced PDF features
  3. Scale with confidence - Review licensing options for your production API needs

Build your .NET PDF API today and streamline document generation across your entire application ecosystem with IronPDF!

Chipego
Chipego Kalinda
  Chat with engineering team now
Software Engineer
Chipego has a natural skill for listening that helps him to comprehend customer issues, and offer intelligent solutions. He joined the Iron Software team in 2023, after studying a Bachelor of Science in Information Technology. IronPDF and IronOCR are the two products Chipego has been focusing on, but his knowledge of ...Read More

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