Improve null dialog identifier handling (#2445)

* Improve null dialog identifier handling (#2262)

* Adding unit test

Fixing nullable reference type declaration of DialogHost methods.

Co-authored-by: Kevin Bost <[email protected]>

Author: Yoooi0

MaterialDesignThemes.Wpf.Tests/DialogHostTests.cs

@@ -333,5 +333,28 @@ public void WhenOpenDialogsAreOpenIsExist()
             DialogHost.Close(id);
             Assert.False(DialogHost.IsDialogOpen(id));
         }
+
+        [StaFact]
+        [Description("Issue 2262")]
+        public async Task WhenOnlySingleDialogHostIdentifierIsNullItShowsDialog()
+        {
+            DialogHost dialogHost2 = new();
+            dialogHost2.ApplyDefaultStyle();
+            dialogHost2.Identifier = Guid.NewGuid();
+
+            try
+            {
+                dialogHost2.RaiseEvent(new RoutedEventArgs(FrameworkElement.LoadedEvent));
+                Task showTask = DialogHost.Show("Content");
+                Assert.True(DialogHost.IsDialogOpen(null));
+                Assert.False(DialogHost.IsDialogOpen(dialogHost2.Identifier));
+                DialogHost.Close(null);
+                await showTask;
+            }
+            finally
+            {
+                dialogHost2.RaiseEvent(new RoutedEventArgs(FrameworkElement.UnloadedEvent));
+            }
+        }
     }
 }

MaterialDesignThemes.Wpf/DialogHost.cs

@@ -159,7 +159,7 @@ static DialogHost()
         ///  Close a modal dialog.
         /// </summary>
         /// <param name="dialogIdentifier"> of the instance where the dialog should be closed. Typically this will match an identifer set in XAML. </param>
-        public static void Close(object dialogIdentifier)
+        public static void Close(object? dialogIdentifier)
             => Close(dialogIdentifier, null);
 
         /// <summary>
@@ -183,7 +183,7 @@ public static void Close(object? dialogIdentifier, object? parameter)
         /// </summary>
         /// <param name="dialogIdentifier">The identifier to use to retrieve the DialogHost</param>
         /// <returns>The DialogSession if one is in process, or null</returns>
-        public static DialogSession? GetDialogSession(object dialogIdentifier)
+        public static DialogSession? GetDialogSession(object? dialogIdentifier)
         {
             DialogHost dialogHost = GetInstance(dialogIdentifier);
             return dialogHost.CurrentSession;
@@ -194,7 +194,7 @@ public static void Close(object? dialogIdentifier, object? parameter)
         /// </summary>
         /// <param name="dialogIdentifier">of the instance where the dialog should be closed. Typically this will match an identifer set in XAML.</param>
         /// <returns></returns>
-        public static bool IsDialogOpen(object dialogIdentifier) => GetDialogSession(dialogIdentifier)?.IsEnded == false;
+        public static bool IsDialogOpen(object? dialogIdentifier) => GetDialogSession(dialogIdentifier)?.IsEnded == false;
 
         private static DialogHost GetInstance(object? dialogIdentifier)
         {
@@ -207,7 +207,7 @@ private static DialogHost GetInstance(object? dialogIdentifier)
                 if (instance.TryGetTarget(out DialogHost? dialogInstance))
                 {
                     dialogInstance.Dispatcher.VerifyAccess();
-                    if (dialogIdentifier is null || Equals(dialogIdentifier, dialogInstance.Identifier))
+                    if (Equals(dialogIdentifier, dialogInstance.Identifier))
                     {
                         targets.Add(dialogInstance);
                     }