How to Retrieve PDF File from Database in ASP.NET Using C# and IronPDF

Fetching PDF from the Database

Here's how you can retrieve a PDF document from your SQL Server database and send it to the browser:

using IronPdf;
using System.Data.SqlClient;
using System.IO;
using Microsoft.AspNetCore.Mvc;

public async Task<IActionResult> RetrievePdfFromDatabase(int documentId, string connectionString)
{
    using var connection = new SqlConnection(connectionString);
    await connection.OpenAsync();
    var query = "SELECT FileName, FileContent FROM PdfDocuments WHERE Id = @Id";
    using var command = new SqlCommand(query, connection);
    command.Parameters.AddWithValue("@Id", documentId);
    using var reader = await command.ExecuteReaderAsync();
    if (reader.Read())
    {
        var fileName = reader["FileName"].ToString();
        var pdfBytes = (byte[])reader["FileContent"];
        var contentType = "application/pdf";
        return new FileContentResult(pdfBytes, contentType)
        {
            FileDownloadName = fileName
        };
    }
    return new NotFoundResult();
}

using IronPdf;
using System.Data.SqlClient;
using System.IO;
using Microsoft.AspNetCore.Mvc;

public async Task<IActionResult> RetrievePdfFromDatabase(int documentId, string connectionString)
{
    using var connection = new SqlConnection(connectionString);
    await connection.OpenAsync();
    var query = "SELECT FileName, FileContent FROM PdfDocuments WHERE Id = @Id";
    using var command = new SqlCommand(query, connection);
    command.Parameters.AddWithValue("@Id", documentId);
    using var reader = await command.ExecuteReaderAsync();
    if (reader.Read())
    {
        var fileName = reader["FileName"].ToString();
        var pdfBytes = (byte[])reader["FileContent"];
        var contentType = "application/pdf";
        return new FileContentResult(pdfBytes, contentType)
        {
            FileDownloadName = fileName
        };
    }
    return new NotFoundResult();
}

This method fetches the PDF file based on its ID, retrieves the binary data, and sends it directly to the client's browser as a downloadable file. The FileContentResult class in ASP.NET Core handles the MIME type and file download name, ensuring that the browser recognizes the file as a PDF document.

Displaying PDF in Browser

To display a PDF directly in the browser without downloading, you can modify the FileContentResult to render the PDF within the browser window:

return new FileContentResult(pdfBytes, "application/pdf");

return new FileContentResult(pdfBytes, "application/pdf");

This line ensures that the PDF is opened in the browser's default PDF viewer, providing a seamless user experience for viewing documents.

Creating the Retrieval Controller

In your ASP.NET Core application, create a controller action to handle PDF retrieval. This controller can be linked to a grid view or called via query string parameters to display or download files:

using IronPdf;
using Microsoft.AspNetCore.Mvc;
using System.Data.SqlClient;
using System;
using System.Threading.Tasks;

[ApiController]
[Route("api/[controller]")]
public class PdfController : ControllerBase
{
    private readonly string _connectionString;
    public PdfController(IConfiguration configuration)
    {
        _connectionString = configuration.GetConnectionString("DefaultConnection");
    }

    [HttpGet("{id}")]
    public async Task<IActionResult> GetPdf(int id)
    {
        try
        {
            // Retrieve PDF documents from database
            byte[] pdfBytes = await RetrievePdfFromDatabase(id);
            if (pdfBytes == null || pdfBytes.Length == 0)
                return NotFound();
            // Load the PDF document using IronPDF for potential modifications
            var pdfDocument = new PdfDocument(pdfBytes);
            // Return file for inline display in browser
            Response.Headers.Add("Content-Disposition", "inline");
            return File(pdfDocument.BinaryData, "application/pdf");
        }
        catch (Exception ex)
        {
            // Handle exception and log error details
            return StatusCode(500, "Error retrieving PDF file");
        }
    }

    private async Task<byte[]> RetrievePdfFromDatabase(int documentId)
    {
        using var connection = new SqlConnection(_connectionString);
        await connection.OpenAsync();
        var query = "SELECT FileContent FROM PdfDocuments WHERE Id = @Id";
        using var command = new SqlCommand(query, connection);
        command.Parameters.AddWithValue("@Id", documentId);
        var result = await command.ExecuteScalarAsync();
        return result as byte[];
    }
}

using IronPdf;
using Microsoft.AspNetCore.Mvc;
using System.Data.SqlClient;
using System;
using System.Threading.Tasks;

[ApiController]
[Route("api/[controller]")]
public class PdfController : ControllerBase
{
    private readonly string _connectionString;
    public PdfController(IConfiguration configuration)
    {
        _connectionString = configuration.GetConnectionString("DefaultConnection");
    }

    [HttpGet("{id}")]
    public async Task<IActionResult> GetPdf(int id)
    {
        try
        {
            // Retrieve PDF documents from database
            byte[] pdfBytes = await RetrievePdfFromDatabase(id);
            if (pdfBytes == null || pdfBytes.Length == 0)
                return NotFound();
            // Load the PDF document using IronPDF for potential modifications
            var pdfDocument = new PdfDocument(pdfBytes);
            // Return file for inline display in browser
            Response.Headers.Add("Content-Disposition", "inline");
            return File(pdfDocument.BinaryData, "application/pdf");
        }
        catch (Exception ex)
        {
            // Handle exception and log error details
            return StatusCode(500, "Error retrieving PDF file");
        }
    }

    private async Task<byte[]> RetrievePdfFromDatabase(int documentId)
    {
        using var connection = new SqlConnection(_connectionString);
        await connection.OpenAsync();
        var query = "SELECT FileContent FROM PdfDocuments WHERE Id = @Id";
        using var command = new SqlCommand(query, connection);
        command.Parameters.AddWithValue("@Id", documentId);
        var result = await command.ExecuteScalarAsync();
        return result as byte[];
    }
}

This controller demonstrates several important concepts. First, it retrieves the binary data from the database using a parameterized query for security. Then, it loads the PDF into IronPDF's PdfDocument object using the FromBytes() method. This step is crucial because it allows you to modify the PDF before sending it to the client. Finally, the File() method with inline: true ensures the PDF is displayed directly in the browser rather than triggering a download, solving the common challenge of retrieving a PDF from a database in ASP.NET using C#.

Implementing Download Functionality

Sometimes users need to download PDF files rather than view them inline. You might add an upload button to save new files or a download link in your grid view. Here's how to modify the response headers for downloading with the correct file name and file path details:

[HttpGet("download/{id}")]
public async Task<IActionResult> DownloadPdf(int id)
{
    // Retrieve stored PDF file from database
    byte[] pdfBytes = await RetrievePdfFromDatabase(id);
    string fileName = await GetFileName(id);
    if (pdfBytes == null || pdfBytes.Length == 0)
        return NotFound("PDF file not found");
    // Load and validate PDF document
    var pdfDocument = new PdfDocument(pdfBytes);
    // Set content disposition for attachment download
    Response.Headers.Append("Content-Disposition", $"attachment; filename={fileName}");
    // Return file for download with default PDF content type
    return File(pdfDocument.BinaryData, "application/pdf", fileName);
}

private async Task<string> GetFileName(int documentId)
{
    using var connection = new SqlConnection(_connectionString);
    await connection.OpenAsync();
    // Query to retrieve PDF file name from database
    var query = "SELECT FileName FROM PdfDocuments WHERE Id = @Id";
    using var command = new SqlCommand(query, connection);
    command.Parameters.AddWithValue("@Id", documentId);
    var result = await command.ExecuteScalarAsync();
    return result as string ?? "document.pdf"; // Default filename if null
}

[HttpGet("download/{id}")]
public async Task<IActionResult> DownloadPdf(int id)
{
    // Retrieve stored PDF file from database
    byte[] pdfBytes = await RetrievePdfFromDatabase(id);
    string fileName = await GetFileName(id);
    if (pdfBytes == null || pdfBytes.Length == 0)
        return NotFound("PDF file not found");
    // Load and validate PDF document
    var pdfDocument = new PdfDocument(pdfBytes);
    // Set content disposition for attachment download
    Response.Headers.Append("Content-Disposition", $"attachment; filename={fileName}");
    // Return file for download with default PDF content type
    return File(pdfDocument.BinaryData, "application/pdf", fileName);
}

private async Task<string> GetFileName(int documentId)
{
    using var connection = new SqlConnection(_connectionString);
    await connection.OpenAsync();
    // Query to retrieve PDF file name from database
    var query = "SELECT FileName FROM PdfDocuments WHERE Id = @Id";
    using var command = new SqlCommand(query, connection);
    command.Parameters.AddWithValue("@Id", documentId);
    var result = await command.ExecuteScalarAsync();
    return result as string ?? "document.pdf"; // Default filename if null
}

By passing the filename parameter to the File() method and setting the content disposition to "attachment", ASP.NET Core prompts the browser to save the PDF to the user's default download folder.

Output

Adding Watermarks to Retrieved PDFs

Here's an example of how to add a watermark to PDF documents as you retrieve them from your database. This is useful when you need to fill PDF pages with additional comments or security markings:

[HttpGet("watermarked/{id}")]
public async Task<IActionResult> GetWatermarkedPdf(int id)
{
    // Retrieve PDF file from database table
    byte[] pdfBytes = await RetrievePdfFromDatabase(id);
    if (pdfBytes == null || pdfBytes.Length == 0)
        return NotFound("Cannot retrieve PDF document");
    // Create new PdfDocument from stored byte array
    var pdfDocument = new PdfDocument(pdfBytes);
    // Add watermark to each page of the PDF document
    string watermarkHtml = "<h2 style='color:red; opacity:0.5'>CONFIDENTIAL</h2>";
    pdfDocument.ApplyWatermark(watermarkHtml, 30, VerticalAlignment.Middle, HorizontalAlignment.Center);
    // Write the modified PDF to response
    return File(pdfDocument.BinaryData, "application/pdf");
}

[HttpGet("watermarked/{id}")]
public async Task<IActionResult> GetWatermarkedPdf(int id)
{
    // Retrieve PDF file from database table
    byte[] pdfBytes = await RetrievePdfFromDatabase(id);
    if (pdfBytes == null || pdfBytes.Length == 0)
        return NotFound("Cannot retrieve PDF document");
    // Create new PdfDocument from stored byte array
    var pdfDocument = new PdfDocument(pdfBytes);
    // Add watermark to each page of the PDF document
    string watermarkHtml = "<h2 style='color:red; opacity:0.5'>CONFIDENTIAL</h2>";
    pdfDocument.ApplyWatermark(watermarkHtml, 30, VerticalAlignment.Middle, HorizontalAlignment.Center);
    // Write the modified PDF to response
    return File(pdfDocument.BinaryData, "application/pdf");
}

Note: IronPDF's watermarking feature accepts HTML content, giving you complete control over the appearance using CSS. The watermark is applied to all pages automatically, and you can adjust rotation, position, and opacity parameters to meet your requirements. This functionality is particularly useful when you need to retrieve a PDF from a database and add security markings or fill the document with additional details.

IronPDF's watermarking feature accepts HTML content, giving you complete control over the appearance using CSS. The watermark is applied to all pages automatically, and you can adjust rotation, position, and opacity to meet your requirements. This functionality is particularly useful when you need to retrieve a PDF from a database and add security markings. For more advanced watermarking techniques, developers often refer to Microsoft's documentation on PDF security.

Cross-Platform Deployment

IronPDF's architecture ensures your PDF retrieval system works consistently across different platforms. Whether you deploy to Windows servers, Linux containers, or cloud platforms like Azure and AWS, the same code runs without modification. The library handles platform-specific rendering details internally, making it ideal for modern containerized deployments using Docker or Kubernetes.

When you create .NET applications that need to retrieve PDF documents from a database table, IronPDF's cross-platform support means you can develop on one platform and deploy to another without changing your code. Simply reference the same NuGet package and use the same API methods across all environments. The library automatically handles URL rendering, HTML conversion, and binary data processing consistently across platforms.