Ensure that PerspexObject bindings are unsubbed.

src/Markup/Perspex.Markup/Data/Plugins/PerspexPropertyAccessorPlugin.cs

@@ -2,9 +2,7 @@
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using System;
-using System.ComponentModel;
 using System.Reactive.Linq;
-using System.Reflection;
 
 namespace Perspex.Markup.Data.Plugins
 {

src/Perspex.Base/Collections/InccDebug.cs

@@ -1,12 +0,0 @@
-// Copyright (c) The Perspex Project. All rights reserved.
-// Licensed under the MIT license. See licence.md file in the project root for full license information.
-
-using System;
-
-namespace Perspex.Collections
-{
-    public interface InccDebug
-    {
-        Delegate[] GetCollectionChangedSubscribers();
-    }
-}

src/Perspex.Base/Collections/PerspexList.cs

@@ -7,6 +7,7 @@ using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.ComponentModel;
 using System.Linq;
+using Perspex.Diagnostics;
 using Perspex.Platform;
 
 namespace Perspex.Collections
@@ -53,7 +54,7 @@ namespace Perspex.Collections
     /// </item>
     /// </list>
     /// </remarks>
-    public class PerspexList<T> : IPerspexList<T>, IList, InccDebug
+    public class PerspexList<T> : IPerspexList<T>, IList, INotifyCollectionChangedDebug
     {
         private List<T> _inner;
         private NotifyCollectionChangedEventHandler _collectionChanged;
@@ -435,7 +436,7 @@ namespace Perspex.Collections
         }
 
         /// <inheritdoc/>
-        Delegate[] InccDebug.GetCollectionChangedSubscribers() => _collectionChanged?.GetInvocationList();
+        Delegate[] INotifyCollectionChangedDebug.GetCollectionChangedSubscribers() => _collectionChanged?.GetInvocationList();
 
         /// <summary>
         /// Raises the <see cref="CollectionChanged"/> event with an add action.

src/Perspex.Base/Diagnostics/INotifyCollectionChangedDebug.cs

@@ -0,0 +1,25 @@
+// Copyright (c) The Perspex Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using System;
+using System.Collections.Specialized;
+using Perspex.Collections;
+
+namespace Perspex.Diagnostics
+{
+    /// <summary>
+    /// Provides a debug interface into <see cref="INotifyCollectionChanged"/> subscribers on
+    /// <see cref="PerspexList{T}"/>
+    /// </summary>
+    public interface INotifyCollectionChangedDebug
+    {
+        /// <summary>
+        /// Gets the subscriber list for the <see cref="INotifyCollectionChanged.CollectionChanged"/>
+        /// event.
+        /// </summary>
+        /// <returns>
+        /// The subscribers or null if no subscribers.
+        /// </returns>
+        Delegate[] GetCollectionChangedSubscribers();
+    }
+}

src/Perspex.Base/Diagnostics/IPerspexObjectDebug.cs

@@ -0,0 +1,22 @@
+// Copyright (c) The Perspex Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using System;
+
+namespace Perspex.Diagnostics
+{
+    /// <summary>
+    /// Provides a debug interface into <see cref="PerspexObject"/>.
+    /// </summary>
+    public interface IPerspexObjectDebug
+    {
+        /// <summary>
+        /// Gets the subscriber list for the <see cref="IPerspexObject.PropertyChanged"/>
+        /// event.
+        /// </summary>
+        /// <returns>
+        /// The subscribers or null if no subscribers.
+        /// </returns>
+        Delegate[] GetPropertyChangedSubscribers();
+    }
+}

src/Perspex.Base/Perspex.Base.csproj

@@ -43,7 +43,7 @@
     <Compile Include="..\Shared\SharedAssemblyInfo.cs">
       <Link>Properties\SharedAssemblyInfo.cs</Link>
     </Compile>
-    <Compile Include="Collections\InccDebug.cs" />
+    <Compile Include="Diagnostics\INotifyCollectionChangedDebug.cs" />
     <Compile Include="Data\AssignBindingAttribute.cs" />
     <Compile Include="Data\BindingOperations.cs" />
     <Compile Include="Data\InstancedBinding.cs" />
@@ -51,6 +51,7 @@
     <Compile Include="Data\IndexerDescriptor.cs" />
     <Compile Include="Collections\PerspexDictionary.cs" />
     <Compile Include="Data\BindingMode.cs" />
+    <Compile Include="Diagnostics\IPerspexObjectDebug.cs" />
     <Compile Include="Diagnostics\PerspexObjectExtensions.cs" />
     <Compile Include="AttachedProperty.cs" />
     <Compile Include="IStyledPropertyAccessor.cs" />
@@ -68,6 +69,7 @@
     <Compile Include="Metadata\XmlnsDefinitionAttribute.cs" />
     <Compile Include="PerspexObjectExtensions.cs" />
     <Compile Include="PropertyMetadata.cs" />
+    <Compile Include="Reactive\WeakPropertyChangedObservable.cs" />
     <Compile Include="StyledProperty.cs" />
     <Compile Include="StyledPropertyBase.cs" />
     <Compile Include="PerspexPropertyRegistry.cs" />
@@ -104,6 +106,7 @@
     <Compile Include="Threading\PerspexScheduler.cs" />
     <Compile Include="Threading\PerspexSynchronizationContext.cs" />
     <Compile Include="Threading\SingleThreadDispatcher.cs" />
+    <Compile Include="Utilities\IWeakSubscriber.cs" />
     <Compile Include="Utilities\MathUtilities.cs" />
     <Compile Include="Utilities\TypeUtilities.cs" />
     <Compile Include="Utilities\WeakSubscriptionManager.cs" />

src/Perspex.Base/PerspexObject.cs

@@ -9,6 +9,7 @@ using System.Reactive.Disposables;
 using System.Reactive.Linq;
 using System.Reactive.Subjects;
 using Perspex.Data;
+using Perspex.Diagnostics;
 using Perspex.Threading;
 using Perspex.Utilities;
 using Serilog;
@@ -22,7 +23,7 @@ namespace Perspex
     /// <remarks>
     /// This class is analogous to DependencyObject in WPF.
     /// </remarks>
-    public class PerspexObject : IPerspexObject, INotifyPropertyChanged
+    public class PerspexObject : IPerspexObject, IPerspexObjectDebug, INotifyPropertyChanged
     {
         /// <summary>
         /// The parent object that inherited values are inherited from.
@@ -40,6 +41,11 @@ namespace Perspex
         /// </summary>
         private PropertyChangedEventHandler _inpcChanged;
 
+        /// <summary>
+        /// Event handler for <see cref="PropertyChanged"/> implementation.
+        /// </summary>
+        private EventHandler<PerspexPropertyChangedEventArgs> _propertyChanged;
+
         /// <summary>
         /// A serilog logger for logging property events.
         /// </summary>
@@ -77,7 +83,11 @@ namespace Perspex
         /// <summary>
         /// Raised when a <see cref="PerspexProperty"/> value changes on this object.
         /// </summary>
-        public event EventHandler<PerspexPropertyChangedEventArgs> PropertyChanged;
+        public event EventHandler<PerspexPropertyChangedEventArgs> PropertyChanged
+        {
+            add { _propertyChanged += value; }
+            remove { _propertyChanged -= value; }
+        }
 
         /// <summary>
         /// Raised when a <see cref="PerspexProperty"/> value changes on this object.
@@ -456,6 +466,11 @@ namespace Perspex
         }
 
         /// <inheritdoc/>
+        Delegate[] IPerspexObjectDebug.GetPropertyChangedSubscribers()
+        {
+            return _propertyChanged?.GetInvocationList();
+        }
+
         /// <summary>
         /// Gets all priority values set on the object.
         /// </summary>
@@ -519,7 +534,7 @@ namespace Perspex
                 OnPropertyChanged(e);
                 property.NotifyChanged(e);
 
-                PropertyChanged?.Invoke(this, e);
+                _propertyChanged?.Invoke(this, e);
 
                 if (_inpcChanged != null)
                 {

src/Perspex.Base/Reactive/WeakPropertyChangedObservable.cs

@@ -45,7 +45,7 @@ namespace Perspex.Reactive
 
             if (_sourceReference.TryGetTarget(out instance))
             {
-                if (_count == 0)
+                if (_count++ == 0)
                 {
                     WeakSubscriptionManager.Subscribe(
                         instance, 

src/Perspex.Controls/Control.cs

@@ -12,6 +12,7 @@ using Perspex.Collections;
 using Perspex.Controls.Primitives;
 using Perspex.Controls.Templates;
 using Perspex.Data;
+using Perspex.Diagnostics;
 using Perspex.Input;
 using Perspex.Interactivity;
 using Perspex.LogicalTree;
@@ -542,7 +543,7 @@ namespace Perspex.Controls
                     child.OnDetachedFromLogicalTree(e);
                 }
 
-                if (((InccDebug)_classes).GetCollectionChangedSubscribers()?.Length > 0)
+                if (((INotifyCollectionChangedDebug)_classes).GetCollectionChangedSubscribers()?.Length > 0)
                 {
                     // TODO: This should be output using a standard logging mechanism.
                     System.Diagnostics.Debug.WriteLine(

tests/Perspex.LeakTests/ControlTests.cs

@@ -9,6 +9,7 @@ using Perspex.Collections;
 using Perspex.Controls;
 using Perspex.Controls.Primitives;
 using Perspex.Controls.Templates;
+using Perspex.Diagnostics;
 using Perspex.Layout;
 using Perspex.Styling;
 using Perspex.UnitTests;
@@ -230,7 +231,7 @@ namespace Perspex.LeakTests
 
                 // The TextBox should have subscriptions to its Classes collection from the
                 // default theme.
-                Assert.NotEmpty(((InccDebug)textBox.Classes).GetCollectionChangedSubscribers());
+                Assert.NotEmpty(((INotifyCollectionChangedDebug)textBox.Classes).GetCollectionChangedSubscribers());
 
                 // Clear the content and ensure the TextBox is removed.
                 window.Content = null;
@@ -238,7 +239,7 @@ namespace Perspex.LeakTests
                 Assert.Null(window.Presenter.Child);
 
                 // Check that the TextBox has no subscriptions to its Classes collection.
-                Assert.Null(((InccDebug)textBox.Classes).GetCollectionChangedSubscribers());
+                Assert.Null(((INotifyCollectionChangedDebug)textBox.Classes).GetCollectionChangedSubscribers());
             }
         }
 

tests/Perspex.Markup.UnitTests/Data/ExpressionObserverTests_PerspexProperty.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Reactive.Linq;
+using Perspex.Diagnostics;
 using Perspex.Markup.Data;
 using Xunit;
 
@@ -24,6 +25,8 @@ namespace Perspex.Markup.UnitTests.Data
             var result = await target.Take(1);
 
             Assert.Equal("foo", result);
+
+            Assert.Null(((IPerspexObjectDebug)data).GetPropertyChangedSubscribers());
         }
 
         [Fact]
@@ -39,6 +42,8 @@ namespace Perspex.Markup.UnitTests.Data
             Assert.Equal(new[] { "foo", "bar" }, result);
 
             sub.Dispose();
+
+            Assert.Null(((IPerspexObjectDebug)data).GetPropertyChangedSubscribers());
         }
 
         [Fact]

tests/Perspex.Styling.UnitTests/SelectorTests_Template.cs

@@ -15,6 +15,7 @@ namespace Perspex.Styling.UnitTests
     using System.Reactive;
     using System.Reactive.Subjects;
     using Collections;
+    using Diagnostics;
     using Controls = Controls.Controls;
 
     public class SelectorTests_Template
@@ -124,7 +125,7 @@ namespace Perspex.Styling.UnitTests
             var border = (Border)target.Object.VisualChildren.Single();
             var selector = new Selector().OfType(templatedControl.Object.GetType()).Class("foo").Template().OfType<Border>();
             var activator = selector.Match(border).ObservableResult;
-            var inccDebug = (InccDebug)styleable.Object.Classes;
+            var inccDebug = (INotifyCollectionChangedDebug)styleable.Object.Classes;
 
             using (activator.Subscribe(_ => { }))
             {