Remove VisualElement finalizer (#918)

* [Controls] Add repo for bugzilla 55365

* Remove finalizer from VisualElement

* Remove unused using directive

* Removing test for 44074

* Update docs

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla55365.cs

@@ -0,0 +1,90 @@
+using System;
+using System.Collections.ObjectModel;
+using System.Collections.Specialized;
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+#if UITEST
+using NUnit.Framework;
+
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Bugzilla, 55365, "~VisualElement crashes with System.Runtime.InteropServices.COMException", PlatformAffected.UWP)]
+	public class Bugzilla55365 : TestContentPage
+	{
+		readonly StackLayout _itemsPanel = new StackLayout();
+		readonly DataTemplate _itemTemplate = new DataTemplate(CreateBoxView);
+		readonly StackLayout _layout = new StackLayout();
+
+#if UITEST
+		[Test]
+		public void ForcingGCDoesNotCrash()
+		{
+			RunningApp.WaitForElement("Clear");
+			RunningApp.Tap("Clear");
+			RunningApp.Tap("Garbage");
+			RunningApp.WaitForElement("Success");
+		}
+#endif
+
+		protected override void Init()
+		{
+			var viewModel = new ObservableCollection<_55365Item>
+			{
+				new _55365Item { Subject = 65 }
+			};
+
+			viewModel.CollectionChanged += OnCollectionChanged;
+
+			_itemsPanel.BindingContext = viewModel;
+
+			foreach (_55365Item item in viewModel)
+			{
+				_itemTemplate.SetValue(BindingContextProperty, item);
+				var view = (View)_itemTemplate.CreateContent();
+				_itemsPanel.Children.Add(view);
+			}
+
+			var clearButton = new Button { Text = "Clear", Command = new Command(o => viewModel.Clear()) };
+			_layout.Children.Add(clearButton);
+
+			var collectButton = new Button { Text = "Garbage", Command = new Command(o =>
+			{
+				GC.Collect();
+				GC.WaitForPendingFinalizers();
+				_layout.Children.Add(new Label {Text = "Success"});
+			}) };
+			_layout.Children.Add(collectButton);
+			_layout.Children.Add(_itemsPanel);
+
+			Content = _layout;
+		}
+
+		static object CreateBoxView()
+		{
+			var boxView1 = new BoxView { HeightRequest = 100, Color = new Color(0.55, 0.23, 0.147) };
+			var setter1 = new Setter { Property = BoxView.ColorProperty, Value = "#FF2879DD" };
+			var trigger1 = new DataTrigger(typeof(BoxView)) { Binding = new Binding("Subject"), Value = 65 };
+			trigger1.Setters.Add(setter1);
+			boxView1.Triggers.Add(trigger1);
+			return boxView1;
+		}
+
+		void OnCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
+		{
+			if (e.Action == NotifyCollectionChangedAction.Reset)
+			{
+				// reset the list
+				_itemsPanel.Children.Clear();
+			}
+		}
+
+		[Preserve(AllMembers = true)]
+		public class _55365Item
+		{
+			public int Subject { get; set; }
+		}
+	}
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems

@@ -282,6 +282,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla53909.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)ListViewNRE.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla55745.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Bugzilla55365.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)_Template.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue1028.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue1075.cs" />

Xamarin.Forms.Core.UnitTests/BehaviorTest.cs

@@ -109,42 +109,5 @@ namespace Xamarin.Forms.Core.UnitTests
 			collection.Remove (behavior);
 			Assert.Null (behavior.AssociatedObject);
 		}
-
-		[Test]
-		//https://bugzilla.xamarin.com/show_bug.cgi?id=44074
-		public void TestBehaviorsAreDetachedBeforeGarbageCollection()
-		{
-			WeakReference weakBindable = null;
-
-			var attachCount = MockBehavior<VisualElement>.AttachCount;
-
-			int i = 0;
-			Action create = null;
-			create = () =>
-			{
-				if (i++ < 1024)
-				{
-					create();
-					return;
-				}
-
-				var bindable = new MockBindable
-				{
-					Behaviors = {
-						new MockBehavior<VisualElement> ()
-					}
-				};
-				weakBindable = new WeakReference(bindable);
-			};
-
-			create();
-
-			GC.Collect();
-			GC.WaitForPendingFinalizers();
-			GC.Collect();
-
-			Assert.False(weakBindable.IsAlive);
-			Assert.AreEqual(attachCount, MockBehavior<VisualElement>.AttachCount);
-		}
 	}
 }

Xamarin.Forms.Core/VisualElement.cs

@@ -796,18 +796,5 @@ namespace Xamarin.Forms
 
 			public bool Result { get; set; }
 		}
-
-		~VisualElement()
-		{
-			if (!GetIsDefault(BehaviorsProperty)) {
-				var behaviors = GetValue(BehaviorsProperty) as AttachedCollection<Behavior>;
-				behaviors.DetachFrom(this);
-			}
-
-			if (!GetIsDefault(TriggersProperty)) {
-				var triggers = GetValue(TriggersProperty) as AttachedCollection<TriggerBase>;
-				triggers.DetachFrom(this);
-			}
-		}
 	}
 }

docs/Xamarin.Forms.Core/Xamarin.Forms/VisualElement.xml

@@ -352,22 +352,6 @@
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
-    <Member MemberName="Finalize">
-      <MemberSignature Language="C#" Value="~VisualElement ();" />
-      <MemberSignature Language="ILAsm" Value=".method familyhidebysig virtual instance void Finalize() cil managed" />
-      <MemberType>Method</MemberType>
-      <AssemblyInfo>
-        <AssemblyVersion>2.0.0.0</AssemblyVersion>
-      </AssemblyInfo>
-      <ReturnValue>
-        <ReturnType>System.Void</ReturnType>
-      </ReturnValue>
-      <Parameters />
-      <Docs>
-        <summary>Finalizer for visual elements.</summary>
-        <remarks>To be added.</remarks>
-      </Docs>
-    </Member>
     <Member MemberName="Focus">
       <MemberSignature Language="C#" Value="public bool Focus ();" />
       <MemberSignature Language="ILAsm" Value=".method public hidebysig instance bool Focus() cil managed" />