Memory Leak in Style with Trigger - fix (#22503)

* Fix #22036

* Added a XAML test #22036

src/Controls/src/Core/Interactivity/EventTrigger.cs

@@ -13,7 +13,7 @@ namespace Microsoft.Maui.Controls
 	public sealed class EventTrigger : TriggerBase
 	{
 		static readonly MethodInfo s_handlerinfo = typeof(EventTrigger).GetRuntimeMethods().Single(mi => mi.Name == "OnEventTriggered" && mi.IsPublic == false);
-		readonly List<BindableObject> _associatedObjects = new List<BindableObject>();
+		readonly List<WeakReference<BindableObject>> _associatedObjects = new List<WeakReference<BindableObject>>();
 
 		EventInfo _eventinfo;
 
@@ -50,13 +50,20 @@ internal override void OnAttachedTo(BindableObject bindable)
 			base.OnAttachedTo(bindable);
 			if (!string.IsNullOrEmpty(Event))
 				AttachHandlerTo(bindable);
-			_associatedObjects.Add(bindable);
+			_associatedObjects.Add(new WeakReference<BindableObject>(bindable));
 		}
 
 		internal override void OnDetachingFrom(BindableObject bindable)
 		{
-			_associatedObjects.Remove(bindable);
-			DetachHandlerFrom(bindable);
+			_associatedObjects.RemoveAll(wr =>
+			{
+				if (wr.TryGetTarget(out var target) && target == bindable)
+				{
+					DetachHandlerFrom(bindable);
+					return true;
+				}
+				return false;
+			});
 			base.OnDetachingFrom(bindable);
 		}
 

src/Controls/tests/Xaml.UnitTests/Issues/Maui22036.xaml

@@ -0,0 +1,4 @@
+<?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="Microsoft.Maui.Controls.Xaml.UnitTests.Maui22036"/>

src/Controls/tests/Xaml.UnitTests/Issues/Maui22036.xaml.cs

@@ -0,0 +1,58 @@
+using System;
+using System.Threading.Tasks;
+using Microsoft.Maui.ApplicationModel;
+using Microsoft.Maui.Controls.Core.UnitTests;
+using Microsoft.Maui.Dispatching;
+using Microsoft.Maui.UnitTests;
+using NUnit.Framework;
+
+namespace Microsoft.Maui.Controls.Xaml.UnitTests;
+
+public partial class Maui22036
+{
+    public Maui22036()
+    {
+        InitializeComponent();
+    }
+
+    public Maui22036(bool useCompiledXaml)
+    {
+        //this stub will be replaced at compile time
+    }
+
+    [TestFixture]
+    class Test
+    {
+        [SetUp]
+        public void Setup()
+        {
+            Application.SetCurrentApplication(new MockApplication());
+            DispatcherProvider.SetCurrent(new DispatcherProviderStub());
+        }
+
+        [TearDown] public void TearDown() => AppInfo.SetCurrent(null);
+
+        [Test]
+        public async Task StyleWithTriggerLeak([Values(false, true)] bool useCompiledXaml)
+        {
+			var style = new Style(typeof(ContentPage));
+            var trigger = new EventTrigger { Event = nameof(Appearing) };
+			trigger.Actions.Add(new EmptyTriggerAction());
+			style.Triggers.Add(trigger);
+
+            Application.Current.Resources.Add(style);
+
+            var pagewr = new WeakReference(new Maui22036(useCompiledXaml));
+            await Task.Delay(10);
+            GC.Collect();
+            Assert.IsNull(pagewr.Target, "Page leaked");
+        }
+    }
+
+	class EmptyTriggerAction : TriggerAction<ContentPage>
+	{
+		protected override void Invoke(ContentPage sender)
+		{
+		}
+	}
+}