fix(textbox): fix TextProperty change propagation in xBind

src/Uno.UI.RuntimeTests/Tests/Windows_UI_Xaml_Controls/Given_TextBox.cs

@@ -47,26 +47,30 @@ namespace Uno.UI.RuntimeTests.Tests.Windows_UI_Xaml_Controls
 	public partial class Given_TextBox
 	{
 		[TestMethod]
-		[DataRow(UpdateSourceTrigger.Default)]
-		[DataRow(UpdateSourceTrigger.PropertyChanged)]
-		[DataRow(UpdateSourceTrigger.Explicit)]
-		[DataRow(UpdateSourceTrigger.LostFocus)]
-		public async Task When_TwoWay_Text_Binding(UpdateSourceTrigger trigger)
+		[DataRow(UpdateSourceTrigger.Default, false)]
+		[DataRow(UpdateSourceTrigger.PropertyChanged, false)]
+		[DataRow(UpdateSourceTrigger.Explicit, false)]
+		[DataRow(UpdateSourceTrigger.LostFocus, false)]
+		[DataRow(UpdateSourceTrigger.Default, true)]
+		[DataRow(UpdateSourceTrigger.LostFocus, true)]
+		public async Task When_TwoWay_Text_Binding(UpdateSourceTrigger trigger, bool xBind)
 		{
 			var SUT = new When_TwoWay_Text_Binding();
-			var tb = trigger switch
+			var tb = (trigger, xBind) switch
 			{
-				UpdateSourceTrigger.Default => SUT.tbTwoWay_triggerDefault,
-				UpdateSourceTrigger.PropertyChanged => SUT.tbTwoWay_triggerPropertyChanged,
-				UpdateSourceTrigger.Explicit => SUT.tbTwoWay_triggerExplicit,
-				UpdateSourceTrigger.LostFocus => SUT.tbTwoWay_triggerLostFocus,
+				(UpdateSourceTrigger.Default, false) => SUT.tbTwoWay_triggerDefault,
+				(UpdateSourceTrigger.PropertyChanged, false) => SUT.tbTwoWay_triggerPropertyChanged,
+				(UpdateSourceTrigger.Explicit, false) => SUT.tbTwoWay_triggerExplicit,
+				(UpdateSourceTrigger.LostFocus, false) => SUT.tbTwoWay_triggerLostFocus,
+				(UpdateSourceTrigger.Default, true) => SUT.tbTwoWay_triggerDefault_xBind,
+				(UpdateSourceTrigger.LostFocus, true) => SUT.tbTwoWay_triggerLostFocus_xBind,
 				_ => throw new Exception("Should not happen."),
 			};
 			var expectedSetCount = 0;
 
 			await UITestHelper.Load(SUT);
 
-			var vm = (When_TwoWay_Text_Binding.VM)tb.DataContext;
+			var vm = xBind ? SUT.VMForXBind : (When_TwoWay_Text_Binding.VM)tb.DataContext;
 
 			Assert.AreNotEqual(tb, FocusManager.GetFocusedElement(SUT.XamlRoot));
 
@@ -75,7 +79,7 @@ public async Task When_TwoWay_Text_Binding(UpdateSourceTrigger trigger)
 
 			// Change text while not focused
 			tb.Text = "Hello";
-			if (trigger != UpdateSourceTrigger.Explicit)
+			if (trigger is UpdateSourceTrigger.PropertyChanged || (trigger is not UpdateSourceTrigger.Explicit && !xBind))
 			{
 				expectedSetCount++;
 			}

src/Uno.UI.RuntimeTests/Tests/Windows_UI_Xaml_Controls/When_TwoWay_Text_Binding.xaml

@@ -13,6 +13,8 @@
 		<TextBox x:Name="tbTwoWay_triggerLostFocus" Text="{Binding VMProperty, Mode=TwoWay, UpdateSourceTrigger=LostFocus}" x:FieldModifier="public" />
 		<TextBox x:Name="tbTwoWay_triggerPropertyChanged" Text="{Binding VMProperty, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" x:FieldModifier="public" />
 		<TextBox x:Name="tbTwoWay_triggerExplicit" Text="{Binding VMProperty, Mode=TwoWay, UpdateSourceTrigger=Explicit}" x:FieldModifier="public" />
+		<TextBox x:Name="tbTwoWay_triggerDefault_xBind" Text="{x:Bind VMForXBind.VMProperty, Mode=TwoWay, UpdateSourceTrigger=Default}" x:FieldModifier="public" />
+		<TextBox x:Name="tbTwoWay_triggerLostFocus_xBind" Text="{x:Bind VMForXBind.VMProperty, Mode=TwoWay, UpdateSourceTrigger=LostFocus}" x:FieldModifier="public" />
 		<Button x:Name="dummyButton" Content="Dummy" x:FieldModifier="public" />
 	</StackPanel>
 </Page>

src/Uno.UI.RuntimeTests/Tests/Windows_UI_Xaml_Controls/When_TwoWay_Text_Binding.xaml.cs

@@ -25,6 +25,8 @@ public string VMProperty
 		public int SetCount { get; private set; }
 	}
 
+	public VM VMForXBind { get; } = new VM();
+
 	public When_TwoWay_Text_Binding()
 	{
 		this.InitializeComponent();

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

@@ -328,7 +328,14 @@ protected virtual void OnTextChanged(DependencyPropertyChangedEventArgs e)
 
 			var focusManager = VisualTree.GetFocusManagerForElement(this);
 			if (focusManager?.FocusedElement != this &&
-				GetBindingExpression(TextProperty) is { ParentBinding.UpdateSourceTrigger: UpdateSourceTrigger.Default or UpdateSourceTrigger.LostFocus } bindingExpression)
+				GetBindingExpression(TextProperty) is
+				{
+					ParentBinding:
+					{
+						IsXBind: false, // NOTE: we UpdateSource in OnTextChanged only when the binding is not an x:Bind. WinUI's generated code for x:Bind contains a simple LostFocus subscription and waits for the next LostFocus even when not focused, unlike regular Bindings.
+						UpdateSourceTrigger: UpdateSourceTrigger.Default or UpdateSourceTrigger.LostFocus
+					}
+				} bindingExpression)
 			{
 				bindingExpression.UpdateSource(Text);
 			}
@@ -994,7 +1001,7 @@ private void OnFocusStateChanged(FocusState oldValue, FocusState newValue, bool
 
 			UpdateButtonStates();
 
-			if (oldValue == FocusState.Unfocused || newValue == FocusState.Unfocused)
+			if (newValue == FocusState.Unfocused)
 			{
 				_hasTextChangedThisFocusSession = false;
 			}