How to Generate and Serve PDF in ASP.NET using iText 7

Introduction

In modern web applications, generating and serving PDF documents is a common requirement. In this tutorial, we will explore how to generate a PDF using iText 7 library in ASP.NET and serve it as a HttpResponseMessage. We will also address a common issue and provide a solution for a corrupted PDF file.

Generating and Serving the PDF

To begin, let’s examine the code snippet provided for generating and serving the PDF using iText 7. We will analyze the key components and make necessary adjustments to ensure a successful PDF generation and delivery.

1. First, ensure that you have the necessary dependencies, including the iText 7 and iText7.pdfHtml libraries, added to your ASP.NET project.
2. The code initializes a StringBuilder object to store the HTML content for the PDF. Modify the StringBuilder as needed to include the desired HTML content.
3. The code then creates a MemoryStream to hold the PDF data. Inside this memory stream, we will perform the PDF generation process.
4. Create a PdfWriter using the MemoryStream and a PdfDocument to work with the PDF structure.
5. If you need to manipulate the header and footer of the PDF document, you can add an event handler using the PdfDocument.AddEventHandler method.
6. Use the HtmlConverter.ConvertToPdf method to convert the HTML content to PDF. This is where the issue arises if the MemoryStream is closed prematurely.

Addressing the Issue

The issue encountered is related to the premature closure of the MemoryStream when using the HtmlConverter.ConvertToPdf method. To resolve this, we need to make a simple adjustment in the code.

1. Instead of using memoryStream.Flush() and memoryStream.Seek(0, SeekOrigin.Begin), replace these lines with byte[] bytes = memoryStream.ToArray(). This ensures that the MemoryStream is accessible even after it is closed.
2. Modify the code to set the HttpResponseMessage content using the MemoryStream directly, without the need for an additional Stream object.

Handling Header/Footer and Closing the Document

To manipulate the header and footer of the PDF document, you can use the PdfDocument and Document objects. However, when using these objects in conjunction with the PdfWriter, ensure that you close the PdfDocument after the conversion process.

To close the PdfDocument, add the following line after the HtmlConverter.ConvertToPdf method:

code
pdfDocument.Close();

Conclusion

In this tutorial, we explored how to generate a PDF using iText 7 in ASP.NET and serve it as a HttpResponseMessage. We addressed the issue of premature MemoryStream closure and provided a solution to ensure successful PDF generation. Additionally, we discussed how to manipulate the header and footer of the PDF document using the PdfDocument and Document objects.

By following these steps and incorporating the necessary adjustments, you can effectively generate and serve PDF documents in your ASP.NET applications using iText 7. Enhance your web application’s functionality and provide a seamless user experience with PDF generation and delivery.