Always propagate the BC to the ControlTemplate

src/Controls/src/Core/ContentView/ContentView.cs

@@ -22,31 +22,27 @@ protected override void OnBindingContextChanged()
 		{
 			base.OnBindingContextChanged();
 
-			IView content = Content;
-
-			if (content == null && (this as IContentView)?.PresentedContent is IView presentedContent)
-				content = presentedContent;
-
-			ControlTemplate controlTemplate = ControlTemplate;
-
-			if (content is BindableObject bindableContent && controlTemplate != null)
-				SetInheritedBindingContext(bindableContent, BindingContext);
+			if (Content is View content)
+			{
+				SetInheritedBindingContext(content, BindingContext);
+			}
 		}
 
 		internal override void OnControlTemplateChanged(ControlTemplate oldValue, ControlTemplate newValue)
 		{
-			if (oldValue == null)
-				return;
-
 			base.OnControlTemplateChanged(oldValue, newValue);
-			View content = Content;
-			ControlTemplate controlTemplate = ControlTemplate;
-			if (content != null && controlTemplate != null)
+
+			if (Content is View content)
 			{
 				SetInheritedBindingContext(content, BindingContext);
 			}
 		}
 
+		internal override void SetChildInheritedBindingContext(Element child, object context)
+		{
+			SetInheritedBindingContext(child, context);
+		}
+
 		object IContentView.Content => Content;
 
 		IView IContentView.PresentedContent => ((this as IControlTemplated).TemplateRoot as IView) ?? Content;

src/Controls/tests/Core.UnitTests/ContentViewUnitTest.cs

@@ -315,7 +315,7 @@ public void PacksContent()
 		}
 
 		[Fact]
-		public void DoesNotInheritBindingContextToTemplate()
+		public void DoesInheritBindingContextToTemplate()
 		{
 			var contentView = new ContentView();
 			var child = new View();
@@ -326,8 +326,38 @@ public void DoesNotInheritBindingContextToTemplate()
 			var bc = "Test";
 			contentView.BindingContext = bc;
 
-			Assert.NotEqual(bc, ((IElementController)contentView).LogicalChildren[0].BindingContext);
-			Assert.Null(((IElementController)contentView).LogicalChildren[0].BindingContext);
+			Assert.Equal(bc, ((IElementController)contentView).LogicalChildren[0].BindingContext);
+		}
+
+		[Fact]
+		public void DoesNotInheritBindingContextToContentFromControlTemplate()
+		{
+			var contentView = new ContentView();
+			var child1 = new View();
+			var child2 = new View();
+
+			contentView.ControlTemplate = new ControlTemplate(typeof(SimpleTemplate));
+			contentView.Content = child1;
+
+			var bcContentView = "Test";
+			var bcSimpleTemplate = "other context";
+			contentView.BindingContext = bcContentView;
+
+			var simpleTemplate = contentView.GetVisualTreeDescendants().OfType<SimpleTemplate>().Single();
+			var cp = contentView.GetVisualTreeDescendants().OfType<ContentPresenter>().Single();
+			simpleTemplate.BindingContext = bcSimpleTemplate;
+
+			Assert.Equal(bcContentView, child1.BindingContext);
+			Assert.Equal(contentView.BindingContext, child1.BindingContext);
+			Assert.Equal(bcSimpleTemplate, simpleTemplate.BindingContext);
+
+			// Change out content and make sure simple templates BC doesn't propagate
+			contentView.Content = child2;
+
+			Assert.Equal(bcContentView, child2.BindingContext);
+			Assert.Equal(contentView.BindingContext, child2.BindingContext);
+			Assert.Equal(bcSimpleTemplate, simpleTemplate.BindingContext);
+			Assert.Equal(bcSimpleTemplate, cp.BindingContext);
 		}
 
 		[Fact]
@@ -346,7 +376,7 @@ public void ContentDoesGetBindingContext()
 		}
 
 		[Fact]
-		public void ContentParentIsNotInsideTempalte()
+		public void ContentParentIsNotInsideTemplate()
 		{
 			var contentView = new ContentView();
 			var child = new View();
@@ -384,5 +414,31 @@ public void ContentView_should_have_the_InternalChildren_correctly_when_Content_
 			Assert.Single(internalChildren);
 			Assert.Same(expected, internalChildren[0]);
 		}
+
+
+		[Fact]
+		public void BindingContextNotLostWhenSwitchingTemplates()
+		{
+			var bc = new object();
+			var contentView = new ContentView()
+			{
+				BindingContext = bc
+			};
+
+
+			contentView.ControlTemplate = new ControlTemplate(typeof(SimpleTemplate));
+
+			var simpleTemplate1 = contentView.GetVisualTreeDescendants().OfType<SimpleTemplate>().Single();
+			contentView.Content = new Label();
+
+			Assert.Same(bc, simpleTemplate1.BindingContext);
+
+			contentView.ControlTemplate = new ControlTemplate(typeof(SimpleTemplate));
+
+			var simpleTemplate2 = contentView.GetVisualTreeDescendants().OfType<SimpleTemplate>().Single();
+
+			Assert.NotSame(simpleTemplate1, simpleTemplate2);
+			Assert.Same(bc, simpleTemplate2.BindingContext);
+		}
 	}
 }