Fix grid not getting invalidated when changing the Height/Width of Row/ColumnDefinitions declared with the short syntax

src/Controls/src/Core/DefinitionCollection.cs

@@ -12,7 +12,14 @@ public class DefinitionCollection<T> : IList<T>, ICollection<T> where T : IDefin
 
 		internal DefinitionCollection() => _internalList = new List<T>();
 
-		internal DefinitionCollection(params T[] items) => _internalList = new List<T>(items);
+		internal DefinitionCollection(params T[] items)
+		{
+			_internalList = new List<T>(items);
+			foreach (var item in items)
+			{
+				(item as IDefinition).SizeChanged += OnItemSizeChanged;
+			}
+		}
 
 		public void Add(T item)
 		{

src/Controls/tests/TestCases.HostApp/Issues/Issues25983.xaml

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             x:Class="Maui.Controls.Sample.Issues.Issue25983">
+
+  <StackLayout>
+    <Button Text="Resize row" AutomationId="resizeRowButton" Clicked="Button_Clicked"></Button>
+    <Button Text="Resize column" AutomationId="resizeColumnButton" Clicked="Button2_Clicked"></Button>
+    <Grid x:Name="grid" AutomationId="grid" RowDefinitions="50,100,200" ColumnDefinitions="100,100">
+      <Label x:Name="resizeRowResultLabel" AutomationId="resizeRowResultLabel" BackgroundColor="Red" Grid.Row="1" Grid.Column="0"></Label>
+      <Label x:Name="resizeColumnResultLabel" AutomationId="resizeColumnResultLabel" BackgroundColor="Blue" Grid.Row="2" Grid.Column="1"></Label>
+    </Grid>
+  </StackLayout>
+
+</ContentPage>

src/Controls/tests/TestCases.HostApp/Issues/Issues25983.xaml.cs

@@ -0,0 +1,21 @@
+namespace Maui.Controls.Sample.Issues
+{
+	[Issue(IssueTracker.Github, 25983, "Issue25983 Grid not getting invalidated when changing the Height/Width of Row/ColumnDefinitions declared with the short syntax", PlatformAffected.All)]
+	public partial class Issue25983 : ContentPage
+	{
+		public Issue25983()
+		{
+			InitializeComponent();
+		}
+
+		private void Button_Clicked(object sender, EventArgs e)
+		{
+			this.grid.RowDefinitions[2].Height = new GridLength(this.grid.RowDefinitions[2].Height.Value + 100, GridUnitType.Absolute);
+		}
+
+		private void Button2_Clicked(object sender, EventArgs e)
+		{
+			this.grid.ColumnDefinitions[1].Width = new GridLength(this.grid.ColumnDefinitions[1].Width.Value + 100, GridUnitType.Absolute);
+		}
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue25983.cs

@@ -0,0 +1,27 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues
+{
+	public class Issue25983 : _IssuesUITest
+	{
+		public Issue25983(TestDevice device) : base(device) { }
+
+		public override string Issue => "Issue25983 Grid not getting invalidated when changing the Height/Width of Row/ColumnDefinitions declared with the short syntax";
+
+		[Test]
+		[Category(UITestCategories.Layout)]
+		public void VerifyGridRowAndColumnSizeInvalidatedCorrectly()
+		{
+			var resizeRowButton = App.WaitForElement("resizeRowButton");
+			var resizeColumnButton = App.WaitForElement("resizeColumnButton");
+
+			resizeRowButton.Click();
+			resizeColumnButton.Click();
+			Task.Delay(500).Wait();
+
+			VerifyScreenshot();
+		}
+	}
+}