Refactor code structure and remove redundant sections for improved readability and maintainability

Fuchs/Controllers/IntranetController.Requests.cs

@@ -369,6 +369,21 @@ public partial class IntranetController
         return await InvoiceIssueResult("Die Rechnung konnte aufgrund eines Fehlers nicht erstellt werden.");
     }
 
+    /// <summary>
+    /// Serves the PDF inline (browser shows it) while advertising the real download filename —
+    /// both a quoted ASCII form and RFC 5987 <c>filename*</c> for spaces/non-ASCII. Works around
+    /// the OCORE FileContentResult helper, whose classic-MVC <c>ExecuteResult(ControllerContext)</c>
+    /// never runs under ASP.NET Core, so the filename was dropped and downloads used the "idoc"
+    /// endpoint segment.
+    /// </summary>
+    private void SetInlinePdfFilename(string filename)
+    {
+        string safe = (filename ?? "").Replace("\"", "").Replace("\r", " ").Replace("\n", " ").Trim();
+        if (safe.Length == 0) return;
+        Response.Headers["Content-Disposition"] =
+            $"inline; filename=\"{safe}\"; filename*=UTF-8''{Uri.EscapeDataString(safe)}";
+    }
+
     private async Task<IActionResult> HandleRequestIdoc(string fn, string id, string code)
     {
         if (!HasForm("id") || string.IsNullOrEmpty(Form("id"))) { _logger.LogWarning("HandleRequestIdoc: missing/empty form field 'id', user={User}", UserAccountID); return StatusCode(404); }
@@ -381,9 +396,13 @@ public partial class IntranetController
             byte[]? ct = Form("create", "0") != "1"
                 ? await _invoices.GetInvoiceFileAsync(fdInv, fdInv.IsDraft, _mfr) is { Length: > 0 } f1 ? f1 : await _invoices.StoreInvoiceDocumentFileAsync(fdInv, fdInv.IsDraft, UserAccountID, DbSec)
                 : _pdf.DocToPdfBytes(_invoices.GenerateInvoicePdf(fdInv, fdInv.IsDraft));
-            return ct != null
-                ? await FileContentResultAsync(ct, "application/pdf", filename, inline: true)
-                : await InvoiceIssueResult("Die Rechnungs-PDF konnte aufgrund eines Fehlers nicht erstellt werden.", fdInv.Id);
+            if (ct == null)
+                return await InvoiceIssueResult("Die Rechnungs-PDF konnte aufgrund eines Fehlers nicht erstellt werden.", fdInv.Id);
+            // Serve inline for the in-browser viewer, but carry the real DocumentName so the browser's
+            // "download" uses "Rechnung R2026-0121.pdf" instead of the "idoc" endpoint segment. (The
+            // OCORE FileContentResult helper drops the filename under ASP.NET Core, so set it here.)
+            SetInlinePdfFilename(filename);
+            return File(ct, "application/pdf");
         }
         var imgcol = await _pdf.DocToImageCollectionAsync(_invoices.GenerateInvoicePdf(fdInv, fdInv.IsDraft));
         return await JSONAsync(new { id = fdInv.Id, img = imgcol.ImgB64Array, total = imgcol.TotalPages });