Add workaround so ItemsRepeater doesn't leak the result of DataTempla…

…te::Load (microsoft/microsoft-ui-xaml#3068)

ModernWpf.Controls/Repeater/ItemsRepeater/ItemsSource/InspectingDataSource.cs

@@ -113,7 +113,7 @@ private void UnListenToCollectionChanges()
         {
             if (m_vector is INotifyCollectionChanged incc)
             {
-                incc.CollectionChanged -= OnCollectionChanged;
+                CollectionChangedEventManager.RemoveHandler(incc, OnCollectionChanged);
             }
         }
 
@@ -122,7 +122,7 @@ private void ListenToCollectionChanges()
             Debug.Assert(m_vector != null);
             if (m_vector is INotifyCollectionChanged incc)
             {
-                incc.CollectionChanged += OnCollectionChanged;
+                CollectionChangedEventManager.AddHandler(incc, OnCollectionChanged);
             }
         }
 

test/ModernWpfTestApp/ApiTests/RepeaterTests/RepeaterTests.cs

@@ -221,7 +221,7 @@ public void VerifyCurrentAnchor()
                   @"<controls:ItemsRepeaterScrollHost Width='400' Height='600'
                      xmlns='http://schemas.microsoft.com/winfx/2006/xaml/presentation'
                      xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
-                     xmlns:controls='using:ModernWpf.Controls'>
+                     xmlns:controls='http://schemas.modernwpf.com/2019'>
                     <controls:ItemsRepeaterScrollHost.Resources>
                         <DataTemplate x:Key='ItemTemplate' >
                             <TextBlock Text='{Binding}' Height='50'/>
@@ -615,5 +615,59 @@ public void VerifyUIElementsInItemsSource()
                 }
             });
         }
+
+
+        [TestMethod]
+        public void VerifyRepeaterDoesNotLeakItemContainers()
+        {
+            ObservableCollection<int> items = new ObservableCollection<int>();
+            for(int i=0;i<10;i++)
+            {
+                items.Add(i);
+            }
+
+            ItemsRepeater repeater = null;
+
+            RunOnUIThread.Execute(() =>
+            {
+                var template = (DataTemplate)XamlReader.Parse("<DataTemplate xmlns='http://schemas.microsoft.com/winfx/2006/xaml/presentation' "
+                    + "xmlns:local='clr-namespace:MUXControlsTestApp.Samples;assembly=MUXControlsTestApp'>"
+                    + "<local:DisposableUserControl Number='{Binding}'/>" 
+                    + "</DataTemplate>");
+                Verify.IsNotNull(template);
+                Verify.AreEqual(0, MUXControlsTestApp.Samples.DisposableUserControl.OpenItems, "Verify we start with 0 DisposableUserControl");
+
+                repeater = new ItemsRepeater() {
+                    ItemsSource = items,
+                    ItemTemplate = template,
+                    VerticalAlignment = VerticalAlignment.Top,
+                    HorizontalAlignment = HorizontalAlignment.Left
+                };
+
+                Content = repeater;
+                
+            });
+
+            IdleSynchronizer.Wait();
+
+            RunOnUIThread.Execute(() =>
+            {
+
+                Verify.IsGreaterThanOrEqual(MUXControlsTestApp.Samples.DisposableUserControl.OpenItems, 10, "Verify we created at least 10 DisposableUserControl");
+
+                // Clear out the repeater and make sure everything gets cleaned up.
+                Content = null;
+                repeater = null;
+            });
+
+            IdleSynchronizer.Wait();
+
+            GC.Collect();
+            GC.WaitForPendingFinalizers();
+            GC.Collect();
+
+            Verify.AreEqual(0, MUXControlsTestApp.Samples.DisposableUserControl.OpenItems, "Verify we cleaned up all the DisposableUserControl that were created");
+        }
+
     }
 }

test/ModernWpfTestApp/Samples/ItemTemplateSamples/DisposableUserControl.xaml

@@ -0,0 +1,14 @@
+<UserControl
+    x:Class="MUXControlsTestApp.Samples.DisposableUserControl"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    mc:Ignorable="d"
+    d:DesignHeight="300"
+    d:DesignWidth="400">
+
+    <Grid>
+        <TextBlock Text="{x:Bind Number}"/>
+    </Grid>
+</UserControl>

test/ModernWpfTestApp/Samples/ItemTemplateSamples/DisposableUserControl.xaml.cs

@@ -0,0 +1,36 @@
+using System.Threading;
+using System.Windows;
+using System.Windows.Controls;
+
+// The User Control item template is documented at https://go.microsoft.com/fwlink/?LinkId=234236
+
+namespace MUXControlsTestApp.Samples
+{
+    public sealed partial class DisposableUserControl : UserControl
+    {
+
+        public int Number
+        {
+            get { return (int)GetValue(NumberProperty); }
+            set { SetValue(NumberProperty, value); }
+        }
+
+        public static readonly DependencyProperty NumberProperty =
+            DependencyProperty.Register("Number", typeof(int), typeof(DisposableUserControl), new PropertyMetadata(-1));
+
+
+        public static int OpenItems { get { return _counter; } }
+        private static int _counter = 0;
+
+        public DisposableUserControl()
+        {
+            Interlocked.Increment(ref _counter);
+            this.InitializeComponent();
+        }
+
+        ~DisposableUserControl()
+        {
+            Interlocked.Decrement(ref _counter);
+        }
+    }
+}

test/ModernWpfTestApp/Samples/ItemTemplateSamples/ItemTemplateDemo.xaml

@@ -16,6 +16,7 @@
             <ColumnDefinition Width="auto" />
             <ColumnDefinition Width="auto" />
             <ColumnDefinition Width="auto" />
+            <ColumnDefinition Width="auto" />
         </Grid.ColumnDefinitions>
         <StackPanel>
             <TextBlock>DataTemplate Sample:</TextBlock>
@@ -98,7 +99,7 @@
                 Width="150">
                 <ScrollViewer>
                     <controls:ItemsRepeater
-                        x:Name="repeater3"
+                        x:Name="repeater4"
                         ItemsSource="{Binding Data}"
                         Layout="{StaticResource stackLayout}">
                         <controls:ItemsRepeater.ItemTemplate>
@@ -123,5 +124,21 @@
                 </ScrollViewer>
             </controls:ItemsRepeaterScrollHost>
         </StackPanel>
+        <StackPanel Grid.Column="4">
+            <TextBlock>DataTemplate clear count checking:</TextBlock>
+            <controls:ItemsRepeaterScrollHost Height="400" Width="150">
+                <ScrollViewer>
+                    <controls:ItemsRepeater x:Name="repeater3" 
+                                            ItemsSource="{x:Bind Numbers}"
+                                            Layout="{StaticResource stackLayout}">
+                        <controls:ItemsRepeater.ItemTemplate>
+                            <DataTemplate>
+                                <local:DisposableUserControl Number="{Bind number, Mode=OneTime}"/>
+                            </DataTemplate>
+                        </controls:ItemsRepeater.ItemTemplate>
+                    </controls:ItemsRepeater>
+                </ScrollViewer>
+            </controls:ItemsRepeaterScrollHost>
+        </StackPanel>
     </Grid>
 </controls:Page>

test/ModernWpfTestApp/Samples/ItemTemplateSamples/ItemTemplateDemo.xaml.cs

@@ -3,6 +3,7 @@
 
 using ModernWpf.Controls;
 using System.Collections.Generic;
+using System.ComponentModel;
 using System.Linq;
 using System.Windows;
 using System.Windows.Controls;
@@ -12,9 +13,17 @@ namespace MUXControlsTestApp.Samples
     public partial class ItemTemplateDemo
     {
         public List<int> Data { get; set; }
+        public List<MyData> Numbers { get; } = new List<MyData>();
+
         public ItemTemplateDemo()
         {
             Data = Enumerable.Range(0, 1000).ToList();
+
+            for(int i=0;i<10;i++)
+            {
+                Numbers.Add(new MyData(i));
+            }
+
             DataContext = this;
             InitializeComponent();
         }
@@ -25,6 +34,16 @@ private void OnSelectTemplateKey(RecyclingElementFactory sender, SelectTemplateE
         }
     }
 
+    public class MyData
+    {
+        public int number;
+
+        public MyData(int number)
+        {
+            this.number = number;
+        }
+    }
+
     public class MySelector : DataTemplateSelector
     {
         public DataTemplate TemplateOdd { get; set; }

test/ModernWpfTestApp/Utilities/RunOnUIThread.cs

@@ -80,19 +80,26 @@ public static void Execute(Dispatcher dispatcher, Action action)
             }
         }
 
-        public async Task WaitForTick()
+        public static void WaitForTick()
         {
-            var renderingEventFired = new TaskCompletionSource<object>();
+            var renderingEvent = new ManualResetEvent(false);
 
-            EventHandler renderingCallback = (sender, arg) =>
+            EventHandler renderingHandler = (object sender, EventArgs args) =>
             {
-                renderingEventFired.TrySetResult(null);
+                renderingEvent.Set();
             };
-            CompositionTarget.Rendering += renderingCallback;
 
-            await renderingEventFired.Task;
+            RunOnUIThread.Execute(() =>
+            {
+                CompositionTarget.Rendering += renderingHandler;
+            });
+
+            renderingEvent.WaitOne();
 
-            CompositionTarget.Rendering -= renderingCallback;
+            RunOnUIThread.Execute(() =>
+            {
+                CompositionTarget.Rendering -= renderingHandler;
+            });
         }
 
     }

test/TestAppUtils/BindExtension.cs

@@ -23,7 +23,7 @@ public BindExtension(string path)
         public PropertyPath Path { get; set; }
 
         [DefaultValue(BindingMode.OneTime)]
-        public BindingMode Mode { get; set; } = BindingMode.OneWay;
+        public BindingMode Mode { get; set; } = BindingMode.OneTime;
 
         [DefaultValue(null)]
         public IValueConverter Converter { get; set; }