MemberAdminWindow: Add feature to export .vcf files

Elwig/Services/MemberService.cs

@@ -493,6 +493,32 @@ namespace Elwig.Services {
                     });
                     Mouse.OverrideCursor = null;
                 }
+            } else if (mode == ExportMode.Vcf) {
+                var d = new SaveFileDialog() {
+                    FileName = "Mitglieder.vcf",
+                    DefaultExt = "vcf",
+                    Filter = "vCard-Datei (*.vcf)|*.vcf",
+                    Title = "Kontakte speichern unter - Elwig"
+                };
+                if (d.ShowDialog() == true) {
+                    Mouse.OverrideCursor = Cursors.Wait;
+                    await Task.Run(async () => {
+                        try {
+                            var members = await query
+                                .OrderBy(m => m.MgNr)
+                                .Include(m => m.BillingAddress)
+                                .Include(m => m.TelephoneNumbers)
+                                .Include(m => m.EmailAddresses)
+                                .AsSplitQuery()
+                                .ToListAsync();
+                            using var exporter = new VCard(d.FileName);
+                            await exporter.ExportAsync(members);
+                        } catch (Exception exc) {
+                            MessageBox.Show(exc.Message, "Fehler", MessageBoxButton.OK, MessageBoxImage.Error);
+                        }
+                    });
+                    Mouse.OverrideCursor = null;
+                }
             } else if (mode == ExportMode.Export) {
                 var d = new SaveFileDialog() {
                     FileName = subject == ExportSubject.Selected ? $"Mitglied_{vm.SelectedMember?.MgNr}.elwig.zip" : $"Mitglieder_{DateTime.Now:yyyy-MM-dd_HH-mm-ss}_{App.ZwstId}.elwig.zip",