feat: adding support for DefaultView property

src/Maui/Prism.Maui/Navigation/Regions/Behaviors/AutoPopulateRegionBehavior.cs

@@ -1,4 +1,4 @@
-using System.ComponentModel;
+using System.ComponentModel;
 using Prism.Ioc;
 
 namespace Prism.Navigation.Regions.Behaviors;
@@ -61,7 +61,7 @@ private void StartPopulatingContent()
                 var registration = registry.Registrations.FirstOrDefault(x => x.View == type);
                 if (registration is not null)
                 {
-                    var view = registry.CreateView(container, registration.Name) as VisualElement;
+                    var view = registry.CreateView(container, registration.Name);
                     Region.Add(view);
                 }
             }

src/Uno/Prism.Uno/Navigation/Regions/NavigationViewRegionAdapter.cs

@@ -27,8 +27,8 @@ protected override void Adapt(IRegion region, NavigationView regionTarget)
         };
     }
 
-    protected override IRegion CreateRegion()
+    protected override IRegion CreateRegion(object regionTarget)
     {
-        return new SingleActiveRegion();
+        return new SingleActiveRegion(regionTarget);
     }
 }

src/Wpf/Prism.Wpf/Navigation/Regions/AllActiveRegion.cs

@@ -5,7 +5,7 @@ namespace Prism.Navigation.Regions
     /// <summary>
     /// Region that keeps all the views in it as active. Deactivation of views is not allowed.
     /// </summary>
-    public class AllActiveRegion : Region
+    public class AllActiveRegion(object target) : Region(target)
     {
         /// <summary>
         /// Gets a readonly view of the collection of all the active views in the region. These are all the added views.

src/Wpf/Prism.Wpf/Navigation/Regions/Behaviors/AutoPopulateRegionBehavior.cs

@@ -44,6 +44,22 @@ private void StartPopulatingContent()
                 AddViewIntoRegion(view);
             }
 
+            if (Region is ITargetAwareRegion targetAware && targetAware.Target is FrameworkElement target 
+                && target.GetValue(RegionManager.DefaultViewProperty) != null)
+            {
+                var defaultView = target.GetValue(RegionManager.DefaultViewProperty);
+                if (defaultView is string targetName)
+                    Region.Add(targetName);
+                else if (defaultView is UIElement element)
+                    Region.Add(element);
+                else if (defaultView is Type type)
+                {
+                    var container = ContainerLocator.Container;
+                    var view = container.Resolve(type);
+                    Region.Add(view);
+                }
+            }
+
             regionViewRegistry.ContentRegistered += OnViewRegistered;
         }
 

src/Wpf/Prism.Wpf/Navigation/Regions/ContentControlRegionAdapter.cs

@@ -53,9 +53,9 @@ protected override void Adapt(IRegion region, ContentControl regionTarget)
         /// Creates a new instance of <see cref="SingleActiveRegion"/>.
         /// </summary>
         /// <returns>A new instance of <see cref="SingleActiveRegion"/>.</returns>
-        protected override IRegion CreateRegion()
+        protected override IRegion CreateRegion(object regionTarget)
         {
-            return new SingleActiveRegion();
+            return new SingleActiveRegion(regionTarget);
         }
     }
 }

src/Wpf/Prism.Wpf/Navigation/Regions/ITargetAwareRegion.cs

@@ -0,0 +1,6 @@
+namespace Prism.Navigation.Regions;
+
+public interface ITargetAwareRegion : IRegion
+{
+    object Target { get; }
+}

src/Wpf/Prism.Wpf/Navigation/Regions/ItemsControlRegionAdapter.cs

@@ -56,9 +56,9 @@ protected override void Adapt(IRegion region, ItemsControl regionTarget)
         /// Creates a new instance of <see cref="AllActiveRegion"/>.
         /// </summary>
         /// <returns>A new instance of <see cref="AllActiveRegion"/>.</returns>
-        protected override IRegion CreateRegion()
+        protected override IRegion CreateRegion(object regionTarget)
         {
-            return new AllActiveRegion();
+            return new AllActiveRegion(regionTarget);
         }
     }
 }

src/Wpf/Prism.Wpf/Navigation/Regions/Region.cs

@@ -8,7 +8,7 @@ namespace Prism.Navigation.Regions
     /// <summary>
     /// Implementation of <see cref="IRegion"/> that allows multiple active views.
     /// </summary>
-    public class Region : IRegion
+    public class Region : ITargetAwareRegion
     {
         private ObservableCollection<ItemMetadata> _itemMetadataCollection;
         private string _name;
@@ -23,13 +23,20 @@ public class Region : IRegion
         /// <summary>
         /// Initializes a new instance of <see cref="Region"/>.
         /// </summary>
-        public Region()
+        /// <param name="target">The target view of the Region</param>
+        public Region(object target)
         {
             Behaviors = new RegionBehaviorCollection(this);
+            Target = target;
 
             _sort = DefaultSortComparison;
         }
 
+        /// <summary>
+        /// Gets the target view of the Region.
+        /// </summary>
+        public object Target { get; }
+
         /// <summary>
         /// Occurs when a property value changes.
         /// </summary>

src/Wpf/Prism.Wpf/Navigation/Regions/RegionAdapterBase.cs

@@ -35,7 +35,7 @@ public IRegion Initialize(T regionTarget, string regionName)
             if (regionName == null)
                 throw new ArgumentNullException(nameof(regionName));
 
-            IRegion region = CreateRegion();
+            IRegion region = CreateRegion(regionTarget);
             region.Name = regionName;
 
             SetObservableRegionOnHostingControl(region, regionTarget);
@@ -121,7 +121,7 @@ protected virtual void AttachBehaviors(IRegion region, T regionTarget)
         /// that will be used to adapt the object.
         /// </summary>
         /// <returns>A new instance of <see cref="IRegion"/>.</returns>
-        protected abstract IRegion CreateRegion();
+        protected abstract IRegion CreateRegion(object regionTarget);
 
         private static T GetCastedObject(object regionTarget)
         {

src/Wpf/Prism.Wpf/Navigation/Regions/RegionManager.cs

@@ -67,6 +67,40 @@ public static string GetRegionName(DependencyObject regionTarget)
             return regionTarget.GetValue(RegionNameProperty) as string;
         }
 
+        /// <summary>
+        /// Sets the DefaultView on the specified region
+        /// </summary>
+        public static readonly DependencyProperty DefaultViewProperty =
+            DependencyProperty.RegisterAttached("DefaultView", typeof(object), typeof(RegionManager), null);
+
+        /// <summary>
+        /// Gets the Default View Instance, Type or Name
+        /// </summary>
+        /// <param name="regionTarget">The Region Target View</param>
+        /// <returns></returns>
+        /// <exception cref="ArgumentNullException"></exception>
+        public static object GetDefaultView(DependencyObject regionTarget)
+        {
+            if (regionTarget == null)
+                throw new ArgumentNullException(nameof(regionTarget));
+
+            return regionTarget.GetValue(DefaultViewProperty);
+        }
+
+        /// <summary>
+        /// Sets the Default Region View Instance, Type or Name.
+        /// </summary>
+        /// <param name="regionTarget">The Region Target.</param>
+        /// <param name="viewNameTypeOrInstance">The view instance, type or name.</param>
+        /// <exception cref="ArgumentNullException"></exception>
+        public static void SetDefaultView(DependencyObject regionTarget, object viewNameTypeOrInstance)
+        {
+            if (regionTarget == null)
+                throw new ArgumentNullException(nameof(regionTarget));
+
+            regionTarget.SetValue(DefaultViewProperty, viewNameTypeOrInstance);
+        }
+
         private static readonly DependencyProperty ObservableRegionProperty =
             DependencyProperty.RegisterAttached("ObservableRegion", typeof(ObservableObject<IRegion>), typeof(RegionManager), null);
 

src/Wpf/Prism.Wpf/Navigation/Regions/SelectorRegionAdapter.cs

@@ -55,9 +55,9 @@ protected override void AttachBehaviors(IRegion region, Selector regionTarget)
         /// Creates a new instance of <see cref="Region"/>.
         /// </summary>
         /// <returns>A new instance of <see cref="Region"/>.</returns>
-        protected override IRegion CreateRegion()
+        protected override IRegion CreateRegion(object regionTarget)
         {
-            return new Region();
+            return new Region(regionTarget);
         }
     }
 }

src/Wpf/Prism.Wpf/Navigation/Regions/SingleActiveRegion.cs

@@ -3,7 +3,7 @@ namespace Prism.Navigation.Regions
     /// <summary>
     /// Region that allows a maximum of one active view at a time.
     /// </summary>
-    public class SingleActiveRegion : Region
+    public class SingleActiveRegion(object target) : Region(target)
     {
         /// <summary>
         /// Marks the specified view as active.

tests/Wpf/Prism.Container.Wpf.Shared/Fixtures/Regions/RegionNavigationContentLoaderFixture.cs

@@ -1,4 +1,4 @@
-using System.Linq;
+using System.Linq;
 using Prism.Ioc;
 using Prism.IocContainer.Wpf.Tests.Support.Mocks.Views;
 using Prism.Navigation.Regions;
@@ -31,7 +31,7 @@ public void ShouldFindCandidateViewInRegion()
 
             // We cannot access the UnityRegionNavigationContentLoader directly so we need to call its
             // GetCandidatesFromRegion method through a navigation request.
-            IRegion testRegion = new Region();
+            IRegion testRegion = new Region(new ContentControl());
 
             MockView view = new MockView();
             testRegion.Add(view);
@@ -54,7 +54,7 @@ public void ShouldFindCandidateViewWithFriendlyNameInRegion()
 
             // We cannot access the Container specific RegionNavigationContentLoader directly so we need to call its
             // GetCandidatesFromRegion method through a navigation request.
-            IRegion testRegion = new Region();
+            IRegion testRegion = new Region(new ContentControl());
 
             var view = _container.Resolve<object>("SomeView") as MockView;
             testRegion.Add(view);

tests/Wpf/Prism.Wpf.Tests/Regions/AllActiveRegionFixture.cs

@@ -12,7 +12,7 @@ public class AllActiveRegionFixture
         public void AddingViewsToRegionMarksThemAsActive()
         {
             ContainerLocator.SetContainerExtension(Mock.Of<IContainerExtension>());
-            IRegion region = new AllActiveRegion();
+            IRegion region = new AllActiveRegion(new ItemsControl());
             var view = new object();
 
             region.Add(view);
@@ -25,7 +25,7 @@ public void DeactivateThrows()
         {
             var ex = Assert.Throws<InvalidOperationException>(() =>
             {
-                IRegion region = new AllActiveRegion();
+                IRegion region = new AllActiveRegion(new ItemsControl());
                 var view = new object();
                 region.Add(view);
 

tests/Wpf/Prism.Wpf.Tests/Regions/Behaviors/ClearChildViewsRegionBehaviorFixture.cs

@@ -15,7 +15,7 @@ public void WhenClearChildViewsPropertyIsNotSet_ThenChildViewsRegionManagerIsNot
         {
             var regionManager = new MockRegionManager();
 
-            var region = new Region();
+            var region = new Region(new ContentControl());
             region.RegionManager = regionManager;
 
             var behavior = new ClearChildViewsRegionBehavior();
@@ -37,7 +37,7 @@ public void WhenClearChildViewsPropertyIsTrue_ThenChildViewsRegionManagerIsClear
         {
             var regionManager = new MockRegionManager();
 
-            var region = new Region();
+            var region = new Region(new ContentControl());
             region.RegionManager = regionManager;
 
             var behavior = new ClearChildViewsRegionBehavior();
@@ -61,7 +61,7 @@ public void WhenRegionManagerChangesToNotNullValue_ThenChildViewsRegionManagerIs
         {
             var regionManager = new MockRegionManager();
 
-            var region = new Region();
+            var region = new Region(new ContentControl());
             region.RegionManager = regionManager;
 
             var behavior = new ClearChildViewsRegionBehavior();

tests/Wpf/Prism.Wpf.Tests/Regions/Behaviors/RegionActiveAwareBehaviorFixture.cs

@@ -131,7 +131,7 @@ public void DoesNotThrowWhenAddingNonActiveAwareDataContexts()
         public void WhenParentViewGetsActivatedOrDeactivated_ThenChildViewIsNotUpdated()
         {
             var scopedRegionManager = new RegionManager();
-            var scopedRegion = new Region { Name = "MyScopedRegion", RegionManager = scopedRegionManager };
+            var scopedRegion = new Region(new ContentControl()) { Name = "MyScopedRegion", RegionManager = scopedRegionManager };
             scopedRegionManager.Regions.Add(scopedRegion);
             var behaviorForScopedRegion = new RegionActiveAwareBehavior { Region = scopedRegion };
             behaviorForScopedRegion.Attach();
@@ -160,7 +160,7 @@ public void WhenParentViewGetsActivatedOrDeactivated_ThenChildViewIsNotUpdated()
         public void WhenParentViewGetsActivatedOrDeactivated_ThenSyncedChildViewIsUpdated()
         {
             var scopedRegionManager = new RegionManager();
-            var scopedRegion = new Region { Name = "MyScopedRegion", RegionManager = scopedRegionManager };
+            var scopedRegion = new Region(new ContentControl()) { Name = "MyScopedRegion", RegionManager = scopedRegionManager };
             scopedRegionManager.Regions.Add(scopedRegion);
             var behaviorForScopedRegion = new RegionActiveAwareBehavior { Region = scopedRegion };
             behaviorForScopedRegion.Attach();
@@ -189,7 +189,7 @@ public void WhenParentViewGetsActivatedOrDeactivated_ThenSyncedChildViewIsUpdate
         public void WhenParentViewGetsActivatedOrDeactivated_ThenSyncedChildViewWithAttributeInVMIsUpdated()
         {
             var scopedRegionManager = new RegionManager();
-            var scopedRegion = new Region { Name = "MyScopedRegion", RegionManager = scopedRegionManager };
+            var scopedRegion = new Region(new ContentControl()) { Name = "MyScopedRegion", RegionManager = scopedRegionManager };
             scopedRegionManager.Regions.Add(scopedRegion);
             var behaviorForScopedRegion = new RegionActiveAwareBehavior { Region = scopedRegion };
             behaviorForScopedRegion.Attach();
@@ -219,7 +219,7 @@ public void WhenParentViewGetsActivatedOrDeactivated_ThenSyncedChildViewWithAttr
         public void WhenParentViewGetsActivatedOrDeactivated_ThenSyncedChildViewModelThatIsNotAFrameworkElementIsNotUpdated()
         {
             var scopedRegionManager = new RegionManager();
-            var scopedRegion = new Region { Name = "MyScopedRegion", RegionManager = scopedRegionManager };
+            var scopedRegion = new Region(new ContentControl()) { Name = "MyScopedRegion", RegionManager = scopedRegionManager };
             scopedRegionManager.Regions.Add(scopedRegion);
             var behaviorForScopedRegion = new RegionActiveAwareBehavior { Region = scopedRegion };
             behaviorForScopedRegion.Attach();
@@ -248,7 +248,7 @@ public void WhenParentViewGetsActivatedOrDeactivated_ThenSyncedChildViewModelTha
         public void WhenParentViewGetsActivatedOrDeactivated_ThenSyncedChildViewNotInActiveViewsIsNotUpdated()
         {
             var scopedRegionManager = new RegionManager();
-            var scopedRegion = new Region { Name = "MyScopedRegion", RegionManager = scopedRegionManager };
+            var scopedRegion = new Region(new ContentControl()) { Name = "MyScopedRegion", RegionManager = scopedRegionManager };
             scopedRegionManager.Regions.Add(scopedRegion);
             var behaviorForScopedRegion = new RegionActiveAwareBehavior { Region = scopedRegion };
             behaviorForScopedRegion.Attach();
@@ -281,7 +281,7 @@ public void WhenParentViewGetsActivatedOrDeactivated_ThenSyncedChildViewNotInAct
         public void WhenParentViewWithoutScopedRegionGetsActivatedOrDeactivated_ThenSyncedChildViewIsNotUpdated()
         {
             var commonRegionManager = new RegionManager();
-            var nonScopedRegion = new Region { Name = "MyRegion", RegionManager = commonRegionManager };
+            var nonScopedRegion = new Region(new ContentControl()) { Name = "MyRegion", RegionManager = commonRegionManager };
             commonRegionManager.Regions.Add(nonScopedRegion);
             var behaviorForScopedRegion = new RegionActiveAwareBehavior { Region = nonScopedRegion };
             behaviorForScopedRegion.Attach();

tests/Wpf/Prism.Wpf.Tests/Regions/Behaviors/RegionMemberLifetimeBehaviorFixture.cs

@@ -21,10 +21,10 @@ public RegionMemberLifetimeBehaviorFixture()
 
         protected virtual void Arrange()
         {
-            this.Region = new Region();
-            this.Behavior = new RegionMemberLifetimeBehavior();
-            this.Behavior.Region = this.Region;
-            this.Behavior.Attach();
+            Region = new Region(new ContentControl());
+            Behavior = new RegionMemberLifetimeBehavior();
+            Behavior.Region = Region;
+            Behavior.Attach();
         }
 
         [Fact]
@@ -257,10 +257,10 @@ public class RegionMemberLifetimeBehaviorAgainstSingleActiveRegionFixture
     {
         protected override void Arrange()
         {
-            this.Region = new SingleActiveRegion();
-            this.Behavior = new RegionMemberLifetimeBehavior();
-            this.Behavior.Region = this.Region;
-            this.Behavior.Attach();
+            Region = new SingleActiveRegion(new ContentControl());
+            Behavior = new RegionMemberLifetimeBehavior();
+            Behavior.Region = Region;
+            Behavior.Attach();
         }
     }
 }

tests/Wpf/Prism.Wpf.Tests/Regions/Behaviors/SelectorItemsSourceSyncRegionBehaviorFixture.cs

@@ -208,7 +208,7 @@ public void ShouldAllowMultipleSelectedItemsForListBox()
 
         private SelectorItemsSourceSyncBehavior CreateBehavior()
         {
-            Region region = new Region();
+            Region region = new Region(new ContentControl());
             Selector selector = new TabControl();
 
             var behavior = new SelectorItemsSourceSyncBehavior();

tests/Wpf/Prism.Wpf.Tests/Regions/ContentControlRegionAdapterFixture.cs

@@ -158,7 +158,7 @@ public TestableContentControlRegionAdapter() : base(null)
 
             private MockPresentationRegion region = new MockPresentationRegion();
 
-            protected override IRegion CreateRegion()
+            protected override IRegion CreateRegion(object regionTarget)
             {
                 return region;
             }

tests/Wpf/Prism.Wpf.Tests/Regions/ItemsControlRegionAdapterFixture.cs

@@ -111,7 +111,7 @@ public TestableItemsControlRegionAdapter() : base(null)
 
             private MockPresentationRegion region = new MockPresentationRegion();
 
-            protected override IRegion CreateRegion()
+            protected override IRegion CreateRegion(object regionTarget)
             {
                 return region;
             }