Quote PDFs in ASP.NET Core

Why quotes become PDFs

A quote is an offer with an expiry, and it gets forwarded to people who will never log into your product. It has to stand alone and it has to be fixed at the moment it was sent. That is the difference between a document and a view of a database, and it is why sales teams keep asking for this.

What a quote has to carry

Before any of the code below matters, the template has to produce a document that is actually a quote. These are the fields that make it one, and the ones a reader or an auditor will look for first.

• a quote reference, which the eventual order will cite
• the validity date, after which the pricing no longer stands
• each line with the price offered, which may not be list price
• any discount shown as a discount rather than folded into the unit price
• the terms attached to the offer: payment schedule, lead time, exclusions

Turning your Razor template into a document

You already have the markup. Await _razorRenderer.RenderViewToStringAsync("Invoice", model) gives you it as a string, which is the only input the render needs. Rendering a Razor view to a string outside the MVC pipeline needs an explicit ActionContext, which is why most projects end up with a small RazorViewToStringRenderer service. Write it once and inject it.

The ASP.NET Core implementation

IHttpClientFactory ships with the runtime, so this adds no dependency. The render happens in an action returning FileStreamResult, and you return File(stream, "application/pdf").

// Controllers/QuoteController.cs
using System.Net.Http.Json;

[ApiController]
public class QuoteController : ControllerBase
{
    private readonly IHttpClientFactory _factory;
    private readonly RazorViewToStringRenderer _razor;

    public QuoteController(IHttpClientFactory factory, RazorViewToStringRenderer razor)
        => (_factory, _razor) = (factory, razor);

    [HttpGet("/quotes/{id}.pdf")]
    public async Task<IActionResult> Pdf(string id, CancellationToken ct)
    {
        var quote = await _quotes.FindAsync(id, ct);
        var html = await _razor.RenderViewToStringAsync("QuotePdf", quote);

        // From the factory. new HttpClient() per request exhausts sockets under
        // load, and the symptom only appears in production.
        var client = _factory.CreateClient("pdfpipe");

        var upstream = await client.PostAsJsonAsync("https://api.pdfpipe.xyz/v1/pdf", new
        {
            html,
            options = new { format = "A4", printBackground = true },
        }, ct);

        upstream.EnsureSuccessStatusCode();

        var stream = await upstream.Content.ReadAsStreamAsync(ct);
        return File(stream, "application/pdf", $"quote-{id}.pdf");
    }
}

The CSS that makes a quote page correctly

The layout problem specific to this document is that optional line items and discount blocks make the length unpredictable, so the signature area must not orphan onto a page of its own. These rules handle it.

/* Backgrounds are dropped unless printBackground is set on the
   request, which is the usual reason a document renders in plain
   black and white when it looked right in the browser. */
@page {
  size: A4;
  margin: 18mm 16mm;
}

table { break-inside: avoid; }
h2    { break-after: avoid; }

What goes wrong in ASP.NET Core

new HttpClient() per request exhausts sockets under sustained load, because each disposed handler leaves a connection in TIME_WAIT. Inject IHttpClientFactory. This is the most common .NET HTTP mistake that only appears in production.

What people try first

Most ASP.NET Core projects reach for PuppeteerSharp, which downloads and supervises a Chromium build from inside your own process, or QuestPDF, which is a fluent layout API rather than a way to render HTML you already have. That works until it is running on more than one machine, at which point the browser becomes the thing you operate rather than the thing you use.

Where the quote lives afterwards

Rendering is the short part. A quote is dead once it expires or converts, so retention is short and driven by the sales system rather than by law. What matters is that the version the customer received is the one you can produce later, because a disputed price is settled by the document that was sent.

Getting the document right

• Check the validity date, since a quote without one is an open-ended commitment.
• Generation is triggered by a salesperson sending it, so latency is felt directly by a person waiting, so size the timeout for that path rather than for a health check.
• These are produced one at a time by a person who is waiting, so latency is felt directly.
• Backgrounds are painted by default here, so a design that uses colour needs nothing set. Only an explicit print_background of false turns them off.

Frequently asked

Related

Other ASP.NET Core documents, and the same quote in other stacks.