Fix for Selector.SelectionChanged is raised twice on updated selection

doc/ReleaseNotes/_ReleaseNotes.md

@@ -125,6 +125,7 @@
  * Ensure that Uno.UI can be used with VS15.8 and earlier (prevent the use of VS15.9 and later String APIs)
  * [Android] Listview Items stay visually in a pressed state,(can click multiple) when you click then scroll down, click another item, and scroll back up
  * 144101 fixed `ListView` group headers messed up on item update
+ * #527 Fix for `Selector.SelectionChanged` is raised twice on updated selection
 
 ## Release 1.42
 

src/SourceGenerators/System.Xaml/System.Xaml/ParsedMarkupExtensionInfo.cs

@@ -141,12 +141,12 @@ private static string RemoveWrappingStringQuotes(string stringValue)
 				// Remove wrapping single quotes.
 				if (stringValue.StartsWith("'") && stringValue.EndsWith("'"))
 				{
-					return stringValue.Trim('\'');
+					return stringValue.Trim(new[] { '\'' });
 				}
 				// Remove wrapping double quotes.
 				else if (stringValue.StartsWith("\"") && stringValue.EndsWith("\""))
 				{
-					return stringValue.Trim('\"');
+					return stringValue.Trim(new[] { '\"' });
 				}
 			}
 

src/Uno.Foundation/Uno.Foundation.csproj

@@ -26,7 +26,7 @@
 	</ItemGroup>
 
 	<ItemGroup>
-		<Analyzer Include="..\Uno.MonoAnalyzers\bin\$(Configuration)\net46\Uno.MonoAnalyzers.dll" />
+		<Analyzer Include="$(MSBuildThisFileDirectory)..\Uno.MonoAnalyzers\bin\$(Configuration)\net46\Uno.MonoAnalyzers.dll" />
 	</ItemGroup>
 
 	<ItemGroup>

src/Uno.MonoAnalyzers/MonoNotSupportedAPIAnalyzer.cs

@@ -72,6 +72,7 @@ public Container(Compilation compilation, MonoNotSupportedAPIAnalyzer owner)
 							"Split",
 							"TrimStart",
 							"TrimEnd",
+							"Trim",
 							"IndexOfAny",
 							"Join",
 							"StartsWith",

src/Uno.UI.Tests/Windows_UI_XAML_Controls/ListViewBaseTests/Given_ListViewBase.cs

@@ -8,15 +8,17 @@
 using Windows.Foundation;
 using Windows.UI.Xaml;
 using Windows.UI.Xaml.Controls;
+using Windows.UI.Xaml.Controls.Primitives;
 using Windows.UI.Xaml.Data;
 
 namespace Uno.UI.Tests.ListViewBaseTests
 {
 	[TestClass]
 	public class Given_ListViewBase
 	{
+
 		[TestMethod]
-		public void When_SingleSelectedItem()
+		public void When_MultiSelectedItem()
 		{
 			var style = new Style(typeof(Windows.UI.Xaml.Controls.ListViewBase))
 			{
@@ -36,22 +38,29 @@ public void When_SingleSelectedItem()
 				Style = style,
 				ItemsPanel = new ItemsPanelTemplate(() => panel),
 				Items = {
-					new Border { Name = "b1" }
+					new Border { Name = "b1" },
+					new Border { Name = "b2" }
 				}
 			};
 
 			// Search on the panel for now, as the name lookup is not properly
 			// aligned on net46.
 			Assert.IsNotNull(panel.FindName("b1"));
+			Assert.IsNotNull(panel.FindName("b2"));
 
-			SUT.SelectedIndex = 0;
+			SUT.SelectionMode = ListViewSelectionMode.Multiple;
+
+			SUT.OnItemClicked(0);
 
-			Assert.IsNotNull(SUT.SelectedItem);
 			Assert.AreEqual(1, SUT.SelectedItems.Count);
+
+			SUT.OnItemClicked(1);
+
+			Assert.AreEqual(2, SUT.SelectedItems.Count);
 		}
 
 		[TestMethod]
-		public void When_MultiSelectedItem()
+		public void When_SingleSelectedItem_Event()
 		{
 			var style = new Style(typeof(Windows.UI.Xaml.Controls.ListViewBase))
 			{
@@ -66,32 +75,89 @@ public void When_MultiSelectedItem()
 
 			var panel = new StackPanel();
 
+			var item = new Border { Name = "b1" };
 			var SUT = new ListViewBase()
 			{
 				Style = style,
 				ItemsPanel = new ItemsPanelTemplate(() => panel),
 				Items = {
-					new Border { Name = "b1" },
-					new Border { Name = "b2" }
+					item
 				}
 			};
 
+			var model = new MyModel
+			{
+				SelectedItem = (object)null
+			};
+
+			SUT.SetBinding(
+				Selector.SelectedItemProperty,
+				new Binding()
+				{
+					Path = "SelectedItem",
+					Source = model,
+					Mode = BindingMode.TwoWay
+				}
+			);
+
 			// Search on the panel for now, as the name lookup is not properly
 			// aligned on net46.
 			Assert.IsNotNull(panel.FindName("b1"));
-			Assert.IsNotNull(panel.FindName("b2"));
 
-			SUT.SelectionMode = ListViewSelectionMode.Multiple;
+			var selectionChanged = 0;
 
-			SUT.OnItemClicked(0);
+			SUT.SelectionChanged += (s, e) =>
+			{
+				selectionChanged++;
+				Assert.AreEqual(item, SUT.SelectedItem);
+
+				// In windows, when programmatically changed, the bindings are updated *after*
+				// the event is raised, but *before* when the SelectedItem is changed from the UI.
+				Assert.IsNull(model.SelectedItem);
+			};
+
+			SUT.SelectedIndex = 0;
 
+			Assert.AreEqual(item, model.SelectedItem);
+
+			Assert.IsNotNull(SUT.SelectedItem);
+			Assert.AreEqual(1, selectionChanged);
 			Assert.AreEqual(1, SUT.SelectedItems.Count);
+		}
 
-			SUT.OnItemClicked(1);
+		[TestMethod]
+		public void When_ResetItemsSource()
+		{
+			var style = new Style(typeof(Windows.UI.Xaml.Controls.ListViewBase))
+			{
+				Setters =  {
+					new Setter<ItemsControl>("Template", t =>
+						t.Template = Funcs.Create(() =>
+							new ItemsPresenter()
+						)
+					)
+				}
+			};
 
-			Assert.AreEqual(2, SUT.SelectedItems.Count);
+			var panel = new StackPanel();
+
+			var SUT = new ListViewBase()
+			{
+				Style = style,
+				ItemsPanel = new ItemsPanelTemplate(() => panel),
+				SelectionMode = ListViewSelectionMode.Single,
+			};
+
+			SUT.ItemsSource = new int[] { 1, 2, 3 };
+			SUT.OnItemClicked(0);
+
+			SUT.ItemsSource = null;
 		}
+	}
 
+	public class MyModel
+	{
+		public object SelectedItem { get; set; }
 	}
 
 	public class MyItemsControl : ItemsControl

src/Uno.UI.Toolkit/Uno.UI.Toolkit.csproj

@@ -108,7 +108,7 @@
 	<Target Name="Publish" />
 
 	<ItemGroup>
-		<Analyzer Include="..\Uno.MonoAnalyzers\bin\$(Configuration)\net46\Uno.MonoAnalyzers.dll" />
+		<Analyzer Include="$(MSBuildThisFileDirectory)..\Uno.MonoAnalyzers\bin\$(Configuration)\net46\Uno.MonoAnalyzers.dll" />
 	</ItemGroup>
 
 	<PropertyGroup>

src/Uno.UI/UI/Xaml/Controls/ListViewBase/ListViewBase.cs

@@ -174,10 +174,25 @@ internal override void OnSelectedItemChanged(object oldSelectedItem, object sele
 			}
 			else
 			{
-				SelectedItems.Clear();
-				SelectedItems.Add(selectedItem);
-
 				base.OnSelectedItemChanged(oldSelectedItem, selectedItem);
+
+				try
+				{
+					_modifyingSelectionInternally = true;
+
+					if (selectedItem != null)
+					{
+						SelectedItems.Update(new[] { selectedItem });
+					}
+					else
+					{
+						SelectedItems.Clear();
+					}
+				}
+				finally
+				{
+					_modifyingSelectionInternally = false;
+				}
 			}
 		}
 

src/Uno.UI/Uno.UI.csproj

@@ -301,7 +301,7 @@
 	</ItemGroup>
 
 	<PropertyGroup> 
-		<UnoUIGeneratorsBinPath>..\SourceGenerators\Uno.UI.SourceGenerators\bin\$(Configuration)</UnoUIGeneratorsBinPath> 
+		<UnoUIGeneratorsBinPath>$(MSBuildThisFileDirectory)..\SourceGenerators\Uno.UI.SourceGenerators\bin\$(Configuration)</UnoUIGeneratorsBinPath> 
 		<UnoUIMSBuildTasksPath>$(MSBuildThisFileDirectory)..\SourceGenerators\Uno.UI.Tasks\bin\$(Configuration)_Shadow</UnoUIMSBuildTasksPath>
 	</PropertyGroup> 
 
@@ -327,7 +327,7 @@
 	</ItemGroup>
 
 	<ItemGroup>
-		<Analyzer Include="..\Uno.MonoAnalyzers\bin\$(Configuration)\net46\Uno.MonoAnalyzers.dll" />
+		<Analyzer Include="$(MSBuildThisFileDirectory)..\Uno.MonoAnalyzers\bin\$(Configuration)\net46\Uno.MonoAnalyzers.dll" />
 	</ItemGroup>
 
 	<ItemGroup>

src/Uno.UWP/Uno.csproj

@@ -68,7 +68,7 @@
 	</ItemGroup>
 
 	<ItemGroup>
-		<Analyzer Include="..\Uno.MonoAnalyzers\bin\$(Configuration)\net46\Uno.MonoAnalyzers.dll" />
+		<Analyzer Include="$(MSBuildThisFileDirectory)..\Uno.MonoAnalyzers\bin\$(Configuration)\net46\Uno.MonoAnalyzers.dll" />
 	</ItemGroup>
 
 	<ItemGroup>