Add Support for NavigateTo within EventToCommandBehavior

src/Forms/Prism.Forms/Xaml/ParentPageAwareExtension.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using Prism.Behaviors;
 using Prism.Properties;
 using Xamarin.Forms;
 using Xamarin.Forms.Xaml;
@@ -85,8 +86,12 @@ private void Initialize()
 
             _targetElement = valueTargetProvider.TargetObject as Element;
 
+            //this is handling the scenario of the extension being used within the EventToCommandBehavior
+            if (_targetElement is null && valueTargetProvider.TargetObject is BehaviorBase<BindableObject> behavior)
+                _targetElement = behavior.AssociatedObject as Element;
+
             if (_targetElement is null)
-                throw new ArgumentNullException(nameof(TargetElement));
+                throw new Exception($"{valueTargetProvider.TargetObject} is not supported");
 
             var parentPage = (Page)GetBindableStack().FirstOrDefault(p => p.GetType()
                                                                            .IsSubclassOf(typeof(Page)));

tests/Forms/Prism.DI.Forms.Tests/Fixtures/Navigation/XamlNavigationFixture.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Threading.Tasks;
 using System.Windows.Input;
+using Prism.Behaviors;
 using Prism.DI.Forms.Tests.Fixtures;
 using Prism.DI.Forms.Tests.Mocks.Internals;
 using Prism.DI.Forms.Tests.Mocks.Views;
@@ -166,5 +167,50 @@ public void UsesMasterDetailPage_WhenParentIsMaster()
             Assert.NotNull(navigateExtension.SourcePage);
             Assert.IsType<MasterDetailPage>(navigateExtension.SourcePage);
         }
+
+
+        [Fact]
+        public async Task ResolvesParentElementFrom_EventToCommandBehavior()
+        {
+            var app = CreateMockApplication();
+
+            Log.Listeners.Clear();
+            var logObserver = new FormsLogObserver();
+            Log.Listeners.Add(logObserver);
+
+            var behavior = new EventToCommandBehavior() { EventName = "ItemTapped" };
+            var layout = new ListView();
+            layout.Behaviors.Add(behavior);
+
+            var serviceProvider = new XamlServiceProvider();
+            serviceProvider.Add(typeof(IProvideValueTarget), new XamlValueTargetProvider(behavior, "Command"));
+
+            var navigateExtension = new NavigateToExtension()
+            {
+                Name = "/AutowireView"
+            };
+            navigateExtension.ProvideValue(serviceProvider);
+
+            app.MainPage = new NavigationPage(new ContentPage
+            {
+                Content = layout
+            });
+
+            Assert.NotNull(layout.Parent);
+            Assert.IsType<ContentPage>(layout.Parent);
+
+            Assert.NotNull(navigateExtension.SourcePage);
+            Assert.True(navigateExtension.CanExecute(null));
+            var ex = await Record.ExceptionAsync(async () =>
+            {
+                navigateExtension.Execute(null);
+                if (navigateExtension.IsNavigating)
+                    await Task.Delay(100);
+            });
+            Assert.Null(ex);
+            Assert.Empty(logObserver.Logs);
+
+            Assert.IsType<AutowireView>(app.MainPage);
+        }
     }
 }