DXApp/DXApp.TemplateKitProject/Pages/Invoices/ViewPdf.cshtml.cs

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using DXApp.TemplateKitProject.Data;
using Microsoft.EntityFrameworkCore;

namespace DXApp.TemplateKitProject.Pages.Invoices;

public class ViewPdfModel : PageModel
{
    private readonly AppDbContext _db;
    private readonly ILogger<ViewPdfModel> _logger;

    public ViewPdfModel(AppDbContext db, ILogger<ViewPdfModel> logger)
    {
        _db = db;
        _logger = logger;
    }

    public async Task<IActionResult> OnGetAsync(int id)
    {
        var invoice = await _db.ZugferdInvoices
            .AsNoTracking()
            .FirstOrDefaultAsync(i => i.Id == id);

        if (invoice is null)
            return NotFound();

        if (string.IsNullOrEmpty(invoice.ResultFilePath))
            return NotFound();

        if (!System.IO.File.Exists(invoice.ResultFilePath))
            return NotFound();

        var bytes = await System.IO.File.ReadAllBytesAsync(invoice.ResultFilePath);
        _logger.LogInformation("ViewPdf: Invoice {Id} ausgeliefert ({Size} Bytes).", id, bytes.Length);

        // Wichtig: keine "attachment" Content-Disposition setzen
        // wir setzen inline (oder lassen es weg) damit Browser im Viewer darstellt
        Response.Headers["Content-Disposition"] = $"inline; filename=\"{Path.GetFileName(invoice.ResultFilePath)}\"";

        return File(bytes, "application/pdf");
    }
}