Add project files.

DXApp.TemplateKitProject/Services/ZugferdExtractorService.cs

@@ -0,0 +1,35 @@
+namespace DXApp.TemplateKitProject.Services
+{
+    using DevExpress.Pdf;
+    using System.Text;
+
+    public class ZugferdExtractorService
+    {
+        private static readonly string[] KnownFileNames =
+        [
+            "zugferd-invoice.xml",
+        "factur-x.xml",
+        "xrechnung.xml"
+        ];
+
+        public string? ExtractXml(Stream pdfStream)
+        {
+            using var processor = new PdfDocumentProcessor();
+            processor.LoadDocument(pdfStream);
+
+            foreach (var attachment in processor.Document.FileAttachments)
+            {
+                bool isZugferd = KnownFileNames.Any(name =>
+                    attachment.FileName.Equals(name, StringComparison.OrdinalIgnoreCase));
+
+                if (isZugferd || attachment.MimeType == "text/xml")
+                {
+                    byte[] data = attachment.Data;
+                    return Encoding.UTF8.GetString(data);
+                }
+            }
+
+            return null; // Kein ZUGFeRD-Anhang gefunden
+        }
+    }
+}