[C] detach Behaviors and Triggers on VE finalization (#555)

* [C] detach Behaviors and Triggers on VE finalization

* update docs

1 files changed, 41 insertions, 1 deletions

diff --git a/Xamarin.Forms.Core.UnitTests/BehaviorTest.cs b/Xamarin.Forms.Core.UnitTests/BehaviorTest.cs
index 78e0cfb0..90217389 100644
--- a/Xamarin.Forms.Core.UnitTests/BehaviorTest.cs
+++ b/Xamarin.Forms.Core.UnitTests/BehaviorTest.cs
@@ -3,8 +3,9 @@ using NUnit.Framework;
 
 namespace Xamarin.Forms.Core.UnitTests
 {
-	internal class MockBehavior<T> : Behavior<T> where T:BindableObject
+	class MockBehavior<T> : Behavior<T> where T:BindableObject
 	{
+		public static int AttachCount { get; set; }
 		public bool attached;
 		public bool detached;
 
@@ -12,11 +13,13 @@ namespace Xamarin.Forms.Core.UnitTests
 		{
 			base.OnAttachedTo (bindable);
 			attached = true;
+			AttachCount++;
 			AssociatedObject = bindable;
 		}
 
 		protected override void OnDetachingFrom (BindableObject bindable)
 		{
+			AttachCount--;
 			detached = true;
 			base.OnDetachingFrom (bindable);
 			AssociatedObject = null;
@@ -106,5 +109,42 @@ 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);
+		}
 	}
 }
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