Fixed Unnecessary SizeChanged Event Triggering (#27476)

* Fixed Fixed Unnecessary SizeChanged Event Triggering

* Added test case

* Added comment on testcase

* Added test case

* Added comment on testcase

* Moved SizeAllocated() within if condition

src/Controls/src/Core/VisualElement/VisualElement.cs

@@ -1756,17 +1756,23 @@ private protected void RefreshInputTransparentProperty()
 
 		void UpdateBoundsComponents(Rect bounds)
 		{
+			if (_frame == bounds)
+				return;
 			_frame = bounds;
 
 			BatchBegin();
 
 			X = bounds.X;
 			Y = bounds.Y;
+			var previousWidth = Width;
+			var previousHeight = Height;
 			Width = bounds.Width;
 			Height = bounds.Height;
-
-			SizeAllocated(Width, Height);
-			SizeChanged?.Invoke(this, EventArgs.Empty);
+			if (previousHeight != Height || previousWidth != Width)
+			{
+				SizeAllocated(Width, Height);
+				SizeChanged?.Invoke(this, EventArgs.Empty);
+			}
 
 			BatchCommit();
 		}

src/Controls/tests/TestCases.HostApp/Issues/Issue27223.cs

@@ -0,0 +1,79 @@
+namespace Maui.Controls.Sample.Issues
+{
+    [Issue(IssueTracker.Github, 27223, "SizeChanged event fires when size hasn't changed", PlatformAffected.UWP)]
+    public class Issue27223 : ContentPage
+    {
+        private int counter = 0;
+        private Label Counter;
+        private Editor ShowSizes;
+        private Editor ShowCoordinates;
+        private VerticalStackLayout stackLayout;
+
+        public Issue27223()
+        {
+            Grid mainGrid = new Grid
+            {
+                ColumnDefinitions =
+                {
+                    new ColumnDefinition { Width = new GridLength(1, GridUnitType.Star) },
+                    new ColumnDefinition { Width = new GridLength(1, GridUnitType.Star) },
+                    new ColumnDefinition { Width = new GridLength(1, GridUnitType.Star) }
+                }
+            };
+
+            Grid leftGrid = new Grid
+            {
+                RowDefinitions =
+                {
+                    new RowDefinition { Height = GridLength.Auto },
+                    new RowDefinition { Height = new GridLength(1, GridUnitType.Star) },
+                    new RowDefinition { Height = GridLength.Auto }
+                }
+            };
+
+            Counter = new Label { AutomationId = "Label" };
+            leftGrid.Children.Add(Counter);
+            Grid.SetRow(Counter, 0);
+
+            stackLayout = new VerticalStackLayout();
+            stackLayout.SizeChanged += VerticalStackLayout_SizeChanged;
+            var button1 = new Button { Text = "button 1", AutomationId = "Button1" };
+            button1.Clicked += Button_Clicked;
+            stackLayout.Children.Add(button1);
+            stackLayout.Children.Add(new Button { Text = "button 2" });
+            stackLayout.Children.Add(new Button { Text = "button 3" });
+            leftGrid.Children.Add(stackLayout);
+            Grid.SetRow(stackLayout, 2);
+
+            ShowSizes = new Editor { BackgroundColor = Colors.SkyBlue, VerticalOptions = LayoutOptions.Fill };
+            ShowCoordinates = new Editor { BackgroundColor = Colors.DarkGoldenrod, VerticalOptions = LayoutOptions.Fill };
+
+            mainGrid.Children.Add(leftGrid);
+            Grid.SetColumn(leftGrid, 0);
+
+            mainGrid.Children.Add(ShowSizes);
+            Grid.SetColumn(ShowSizes, 1);
+
+            mainGrid.Children.Add(ShowCoordinates);
+            Grid.SetColumn(ShowCoordinates, 2);
+
+            Content = mainGrid;
+        }
+
+        private void Button_Clicked(object sender, EventArgs e)
+        {
+#if WINDOWS
+			Window.Height = 500;
+#endif
+        }
+
+        private void VerticalStackLayout_SizeChanged(object sender, EventArgs e)
+        {
+            if (sender is VerticalStackLayout ctrl)
+            {
+                counter++;
+                Counter.Text = $"resized {counter} times";
+            }
+        }
+    }
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue27223.cs

@@ -0,0 +1,28 @@
+#if WINDOWS // mac does not respond to the window size change. so, ignored test on mac.
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues
+{
+    public class Issue27223 : _IssuesUITest
+    {
+        public Issue27223(TestDevice testDevice) : base(testDevice)
+        {
+        }
+
+        public override string Issue => "SizeChanged event fires when size hasn't changed";
+
+        [Test]
+        [Category(UITestCategories.Layout)]
+        public void SizeChangedOnlyFiresWhenSizeChanges()
+        {
+            App.WaitForElement("Label");
+            var initialValue = App.FindElement("Label").GetText();
+            App.Tap("Button1");
+            var finalValue = App.FindElement("Label").GetText();
+            Assert.That(initialValue, Is.EqualTo(finalValue));
+        }
+    }
+}
+#endif