Ensure that Grid is propagating the BindingContext to the row/col def…

…initions (#7301)

Fixes #4609

src/Controls/src/Core/Layout/Grid.cs

@@ -369,6 +369,8 @@ void DefinitionsChanged(object sender, EventArgs args)
 			_rowDefs = null;
 			_colDefs = null;
 
+			UpdateRowColumnBindingContexts();
+
 			InvalidateMeasure();
 		}
 
@@ -378,6 +380,29 @@ protected override void InvalidateMeasure()
 			(this as IView)?.InvalidateMeasure();
 		}
 
+		protected override void OnBindingContextChanged()
+		{
+			base.OnBindingContextChanged();
+			UpdateRowColumnBindingContexts();
+		}
+
+		void UpdateRowColumnBindingContexts()
+		{
+			var bindingContext = BindingContext;
+
+			RowDefinitionCollection rowDefs = RowDefinitions;
+			for (var i = 0; i < rowDefs.Count; i++)
+			{
+				SetInheritedBindingContext(rowDefs[i], bindingContext);
+			}
+
+			ColumnDefinitionCollection colDefs = ColumnDefinitions;
+			for (var i = 0; i < colDefs.Count; i++)
+			{
+				SetInheritedBindingContext(colDefs[i], bindingContext);
+			}
+		}
+
 		class GridInfo
 		{
 			public int Row { get; set; }

src/Controls/tests/Core.UnitTests/Layouts/GridLayoutTests.cs

@@ -128,5 +128,61 @@ static void AssertInvalidated(IViewHandler handler)
 		{
 			handler.Received().Invoke(Arg.Is(nameof(IView.InvalidateMeasure)), Arg.Any<object>());
 		}
+
+		[Test]
+		public void RowDefinitionsGetBindingContext() 
+		{
+			var def = new RowDefinition();
+			var def2 = new RowDefinition();
+
+			var grid = new Grid()
+			{
+				RowDefinitions = new RowDefinitionCollection
+				{
+					def
+				}
+			};
+
+			var context = new object();
+
+			Assert.That(def.BindingContext, Is.Null);
+			Assert.That(def2.BindingContext, Is.Null);
+
+			grid.BindingContext = context;
+
+			Assert.That(def.BindingContext, Is.EqualTo(context));
+
+			grid.RowDefinitions.Add(def2);
+
+			Assert.That(def2.BindingContext, Is.EqualTo(context));
+		}
+
+		[Test]
+		public void ColumnDefinitionsGetBindingContext()
+		{
+			var def = new ColumnDefinition();
+			var def2 = new ColumnDefinition();
+
+			var grid = new Grid()
+			{
+				ColumnDefinitions = new ColumnDefinitionCollection
+				{
+					def
+				}
+			};
+
+			var context = new object();
+
+			Assert.That(def.BindingContext, Is.Null);
+			Assert.That(def2.BindingContext, Is.Null);
+
+			grid.BindingContext = context;
+
+			Assert.That(def.BindingContext, Is.EqualTo(context));
+
+			grid.ColumnDefinitions.Add(def2);
+
+			Assert.That(def2.BindingContext, Is.EqualTo(context));
+		}
 	}
 }