WinUI: Fix several problems with WinUI PKI security sample (#1485)

src/WinUI/ArcGIS.WinUI.Viewer/Samples/Security/CertificateAuthenticationWithPki/CertificateAuthenticationWithPKI.xaml.cs

@@ -7,6 +7,7 @@
 // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific
 // language governing permissions and limitations under the License.
 
+using CommunityToolkit.WinUI;
 using Esri.ArcGISRuntime.Portal;
 using Esri.ArcGISRuntime.Security;
 using Microsoft.UI.Xaml;
@@ -33,7 +34,17 @@ public CertificateAuthenticationWithPKI()
  InitializeComponent();
  }
 
- public async Task<Credential> CreateCertCredentialAsync(CredentialRequestInfo info)
+ private async Task<Credential> HandleCredentialRequest(CredentialRequestInfo info)
+ {
+ if (info.AuthenticationType == AuthenticationType.Certificate)
+ {
+ // ChallengeHandler may be called from a background thread, so we need to switch to the UI thread to show the dialog.
+ return await DispatcherQueue.EnqueueAsync(async () => await CreateCertCredentialAsync(info));
+ }
+ return null;
+ }
+
+ private async Task<Credential> CreateCertCredentialAsync(CredentialRequestInfo info)
  {
  // Handle challenges for a secured resource by prompting for a client certificate.
  Credential credential = null;
@@ -55,6 +66,7 @@ public async Task<Credential> CreateCertCredentialAsync(CredentialRequestInfo in
 
  // Create a list view for rendering the list.
  ListView listview = new ListView();
+ listview.SelectionMode = ListViewSelectionMode.Single;
 
  // Use a template defined as a resource in XAML.
  listview.ItemTemplate = (DataTemplate)this.Resources["CertificateTemplate"];
@@ -66,6 +78,7 @@ public async Task<Credential> CreateCertCredentialAsync(CredentialRequestInfo in
  dialog.Content = listview;
 
  // Display the dialog.
+ dialog.XamlRoot = this.XamlRoot;
  await dialog.ShowAsync();
 
  // Make sure the user chose a certificate.
@@ -101,7 +114,7 @@ private async void Button_Click(object sender, RoutedEventArgs e)
  _serverUrl = PortalUrlTextbox.Text;
 
  // Configure the authentication manager.
- AuthenticationManager.Current.ChallengeHandler = new ChallengeHandler(CreateCertCredentialAsync);
+ AuthenticationManager.Current.ChallengeHandler = new ChallengeHandler(HandleCredentialRequest);
 
  // Create the portal.
  ArcGISPortal portal = await ArcGISPortal.CreateAsync(new Uri(_serverUrl));