Add DevExpress Document Viewer page and dependencies

Updated `_ViewImports.cshtml` to include DevExpress and DevExtreme tag helpers. Created `DocumentViewerDevExpress.cshtml` for displaying a DevExpress Document Viewer with necessary CDN links. Implemented the corresponding code-behind in `DocumentViewerDevExpress.cshtml.cs` to handle model binding and report key generation.

DXApp.TemplateKitProject/Controllers/DocumentViewerController.cs

@@ -0,0 +1,16 @@
+using Microsoft.AspNetCore.Mvc;
+using DevExpress.AspNetCore.Reporting.WebDocumentViewer;
+using DevExpress.AspNetCore.Reporting.WebDocumentViewer.Native.Services;
+
+namespace DXApp.TemplateKitProject.Controllers
+{
+    [Route("DocumentViewer")]
+    public class DocumentViewerController : WebDocumentViewerController
+    {
+        // Hier den erwarteten DevExpress-Service injizieren und an die Basisklasse weitergeben
+        public DocumentViewerController(IWebDocumentViewerMvcControllerService controllerService)
+            : base(controllerService)
+        {
+        }
+    }
+}

DXApp.TemplateKitProject/DXApp.TemplateKitProject.csproj

@@ -29,8 +29,4 @@
     <PackageReference Include="Microsoft.Web.LibraryManager.Build" Version="3.0.71" />
   </ItemGroup>
 
-  <ItemGroup>
-    <Folder Include="Controllers\" />
-  </ItemGroup>
-
 </Project>

DXApp.TemplateKitProject/Pages/Invoices/Details.cshtml

@@ -16,10 +16,10 @@
 
 @if (!string.IsNullOrEmpty(Model.Invoice?.ResultFilePath))
 {
-    <button class="btn btn-primary mb-3 ms-2"
+    <a class="btn btn-primary mb-3 ms-2"
-            onclick="openPdfViewer(@Model.Invoice.Id)">
+       href="/Invoices/DocumentViewer?id=@Model.Invoice.Id">
         <i class="dx-icon-pdffile"></i> Ergebnis anzeigen
-    </button>
+    </a>
 }
 
 @if (Model.Invoice is null)

DXApp.TemplateKitProject/Pages/Invoices/DocumentViewer.cshtml

@@ -0,0 +1,33 @@
+@page
+@model DXApp.TemplateKitProject.Pages.Invoices.DocumentViewerModel
+@{
+    ViewData["Title"] = "Dokument Viewer";
+    var pdfUrl = Model.PdfUrl;
+}
+
+<div class="container-fluid" style="height:100vh; padding:0;">
+    <div class="d-flex align-items-center justify-content-between p-3 border-bottom">
+        <h5 class="m-0">Rechnung @Model.Id - Dokument</h5>
+        <div>
+            <a class="btn btn-secondary me-2" href="/Invoices">Zurück zur Übersicht</a>
+            <!-- Später: Button um DevExpress Viewer zu öffnen -->
+            <a class="btn btn-outline-primary" href="/Invoices/DocumentViewerDevExpress?id=@Model.Id">
+                DevExpress Viewer (experimental)
+            </a>
+        </div>
+    </div>
+
+    <div style="height:calc(100vh - 64px);">
+        @* Solide, funktionierende Baseline: Browser-internen PDF-Renderer verwenden *@
+        <iframe id="pdf-viewer-iframe"
+                src="@pdfUrl"
+                style="width:100%; height:100%; border: none;"
+                title="PDF Viewer"></iframe>
+    </div>
+
+    @* Hinweis:
+       - Diese Seite zeigt aktuell das PDF per einfachem iframe (funktioniert zuverlässig).
+       - Nächster Commit: wir ersetzen iframe durch DevExpress WebDocumentViewer oder laden diesen zusätzlich.
+       - Der Link "DevExpress Viewer (experimental)" ist ein Platzhalter; wir implementieren die Route /Invoices/DocumentViewerDevExpress in einem der nächsten Schritte.
+    *@
+</div>

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

@@ -0,0 +1,17 @@
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Mvc.RazorPages;
+
+namespace DXApp.TemplateKitProject.Pages.Invoices;
+
+public class DocumentViewerModel : PageModel
+{
+    [BindProperty(SupportsGet = true)]
+    public int Id { get; set; }
+
+    public string PdfUrl => $"/Invoices/ViewPdf?id={Id}";
+
+    public void OnGet()
+    {
+        // Keine serverseitige Logik nötig für die erste Version.
+    }
+}

DXApp.TemplateKitProject/Pages/Invoices/DocumentViewerDevExpress.cshtml

@@ -0,0 +1,32 @@
+@page
+@model DXApp.TemplateKitProject.Pages.Invoices.DocumentViewerDevExpressModel
+@{
+    ViewData["Title"] = "DevExpress Document Viewer";
+}
+
+@* Dev: Für schnelle Tests verwenden wir die CDN-Assets.
+   In Production bitte lokal hosten und Lizenz einbinden. *@
+<link rel="stylesheet" href="https://cdn3.devexpress.com/jslib/25.2.7/css/dx.common.css" />
+<link rel="stylesheet" href="https://cdn3.devexpress.com/jslib/25.2.7/css/dx.light.css" />
+<script src="https://cdn3.devexpress.com/jslib/25.2.7/js/dx.all.js"></script>
+<script src="https://cdn3.devexpress.com/jslib/25.2.7/js/dx.aspnet.data.js"></script>
+
+<div class="container-fluid" style="height:100vh; padding:0;">
+    <div class="d-flex align-items-center justify-content-between p-3 border-bottom">
+        <h5 class="m-0">DevExpress Viewer — Rechnung @Model.Id</h5>
+        <div>
+            <a class="btn btn-secondary me-2" href="/Invoices">Zurück zur Übersicht</a>
+            <a class="btn btn-outline-secondary" href="/Invoices/DocumentViewer?id=@Model.Id">Baseline Viewer</a>
+        </div>
+    </div>
+
+    <div style="height:calc(100vh - 64px);">
+        @* KORRIGIERTE SYNTAX: Der WebDocumentViewer-Helper wird direkt aufgerufen. *@
+        @(Html.DevExpress().WebDocumentViewer()
+                .Name("WebDocumentViewer")
+                .Height("100%")
+                .Width("100%")
+                .Bind(Model.ReportKey)
+                )
+    </div>
+</div>

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

@@ -0,0 +1,16 @@
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Mvc.RazorPages;
+
+namespace DXApp.TemplateKitProject.Pages.Invoices;
+
+public class DocumentViewerDevExpressModel : PageModel
+{
+    [BindProperty(SupportsGet = true)]
+    public int Id { get; set; }
+
+    public string ReportKey => $"invoice-{Id}";
+
+    public void OnGet()
+    {
+    }
+}

DXApp.TemplateKitProject/Pages/Invoices/ViewPdf.cshtml

@@ -1,2 +1,6 @@
 @page
 @model DXApp.TemplateKitProject.Pages.Invoices.ViewPdfModel
+@{
+    Layout = "_Layout";
+    // Diese Seite liefert keinen HTML-Content; der Handler gibt die PDF zurück.
+}

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

@@ -1,24 +1,43 @@
-using DXApp.TemplateKitProject.Data;
+using Microsoft.AspNetCore.Mvc;
-using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.Mvc.RazorPages;
+using DXApp.TemplateKitProject.Data;
 using Microsoft.EntityFrameworkCore;
 
 namespace DXApp.TemplateKitProject.Pages.Invoices;
 
-public class ViewPdfModel(AppDbContext db) : PageModel
+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
+        var invoice = await _db.ZugferdInvoices
+            .AsNoTracking()
             .FirstOrDefaultAsync(i => i.Id == id);
 
-        if (invoice is null || string.IsNullOrEmpty(invoice.ResultFilePath))
+        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");
     }
 }

DXApp.TemplateKitProject/Pages/_ViewImports.cshtml

@@ -1,4 +1,10 @@
 @using DXApp.TemplateKitProject
+@using DXApp.TemplateKitProject.Pages
 @namespace DXApp.TemplateKitProject.Pages
 @addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers
+
+@* --- DevExpress & DevExtreme Integration --- *@
+@using DevExpress.AspNetCore
+@using DevExpress.AspNetCore.Reporting
 @using DevExtreme.AspNet.Mvc
+@addTagHelper *, DevExtreme.AspNet.Core

DXApp.TemplateKitProject/Program.cs

@@ -8,6 +8,9 @@ using DevExpress.XtraReports.Web.Extensions;
 
 var builder = WebApplication.CreateBuilder(args);
 
+// MVC-Controller hinzufügen (benötigt für DevExpress WebDocumentViewer)
+builder.Services.AddControllersWithViews();
+
 builder.Services.AddRazorPages();
 
 // DevExpress Controls und Reporting Services
@@ -52,5 +55,8 @@ app.UseDevExpressControls();
 
 app.UseRouting();
 app.UseAuthorization();
+
+// Controller-Routen verfügbar machen (wichtig für DevExpress WebDocumentViewer)
+app.MapControllers();
 app.MapRazorPages();
 app.Run();