[release/9.0.1xx] [XC] Propagate x:DataType from parent scope to "standalone bindings"

src/Controls/src/Build.Tasks/SetPropertiesVisitor.cs

@@ -305,7 +305,7 @@ public static IEnumerable<Instruction> ProvideValue(VariableDefinitionReference
 					bool skipBindingCompilation = hasSource && !context.CompileBindingsWithSource;
 					if (!skipBindingCompilation)
 					{
-						if (TryCompileBindingPath(node, context, vardefref.VariableDefinition, bindingExtensionType.Value, isStandaloneBinding: bpRef is null, out var instructions))
+						if (TryCompileBindingPath(node, context, vardefref.VariableDefinition, bindingExtensionType.Value, out var instructions))
 						{
 							foreach (var instruction in instructions)
 								yield return instruction;
@@ -421,7 +421,7 @@ public static IEnumerable<Instruction> ProvideValue(VariableDefinitionReference
 		}
 
 		//Once we get compiled IValueProvider, this will move to the BindingExpression
-		static bool TryCompileBindingPath(ElementNode node, ILContext context, VariableDefinition bindingExt, (string, string, string) bindingExtensionType, bool isStandaloneBinding, out IEnumerable<Instruction> instructions)
+		static bool TryCompileBindingPath(ElementNode node, ILContext context, VariableDefinition bindingExt, (string, string, string) bindingExtensionType, out IEnumerable<Instruction> instructions)
 		{
 			instructions = null;
 
@@ -456,13 +456,6 @@ static bool TryCompileBindingPath(ElementNode node, ILContext context, VariableD
 				{
 					break;
 				}
-				else if (isStandaloneBinding)
-				{
-					// For standalone bindings we don't allow inheriting the x:DataType from its parents.
-					// A standalone binding is a binding instance which is not immediately applied through `SetBinding(...)`
-					// but it is applied later (for example it is applied to items in a collection).
-					break;
-				}
 
 				if (n.XmlType.Name == nameof(Microsoft.Maui.Controls.DataTemplate)
 					&& n.XmlType.NamespaceUri == XamlParser.MauiUri)

src/Controls/tests/Xaml.UnitTests/Issues/Maui23989.xaml.cs

@@ -38,7 +38,7 @@ public void Setup()
         public void ItemDisplayBindingWithoutDataTypeFails([Values(false, true)] bool useCompiledXaml)
         {
             if (useCompiledXaml)
-                Assert.Throws(new BuildExceptionConstraint(12, 13, s => s.Contains("0022", StringComparison.Ordinal)), ()=> MockCompiler.Compile(typeof(Maui23989), null, true));
+                Assert.Throws(new BuildExceptionConstraint(12, 13, s => s.Contains("0045", StringComparison.Ordinal)), ()=> MockCompiler.Compile(typeof(Maui23989), null, true));
 
             var layout = new Maui23989(useCompiledXaml);
             //without x:DataType, bindings aren't compiled

src/Controls/tests/Xaml.UnitTests/Issues/Maui25141.xaml

@@ -0,0 +1,43 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             xmlns:local="clr-namespace:Microsoft.Maui.Controls.Xaml.UnitTests"
+             x:DataType="local:Maui25141ViewModel"
+             x:Class="Microsoft.Maui.Controls.Xaml.UnitTests.Maui25141">
+    <ContentPage.Resources>
+        <MultiBinding
+            x:Key="MultiBinding"
+            Mode="TwoWay">
+            <Binding Path="Text"/>
+        </MultiBinding>
+
+        <DataTrigger
+            x:Key="DataTrigger"
+            Binding="{Binding TriggerFlag}"
+            TargetType="Label"
+            Value="True">
+            <Setter Property="Text" Value="TRIGGERED" />
+        </DataTrigger>
+    </ContentPage.Resources>
+
+    <StackLayout>
+        <Label x:Name="LabelA">
+            <Label.Text>
+                <MultiBinding Mode="TwoWay">
+                    <Binding Path="Text"/>
+                </MultiBinding>
+            </Label.Text>
+        </Label>
+
+        <Label x:Name="LabelB">
+            <Label.Triggers>
+                <DataTrigger
+                    Binding="{Binding TriggerFlag}"
+                    TargetType="Button"
+                    Value="True">
+            <Setter Property="Text" Value="TRIGGERED" />
+                </DataTrigger>
+            </Label.Triggers>
+        </Label>
+    </StackLayout>
+</ContentPage>

src/Controls/tests/Xaml.UnitTests/Issues/Maui25141.xaml.cs

@@ -0,0 +1,86 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Diagnostics;
+using System.Globalization;
+using System.Linq;
+using Microsoft.Maui.ApplicationModel;
+using Microsoft.Maui.Controls.Core.UnitTests;
+using Microsoft.Maui.Controls.Shapes;
+using Microsoft.Maui.Devices;
+using Microsoft.Maui.Dispatching;
+
+using Microsoft.Maui.Graphics;
+using Microsoft.Maui.UnitTests;
+using NUnit.Framework;
+
+namespace Microsoft.Maui.Controls.Xaml.UnitTests;
+
+[XamlCompilation(XamlCompilationOptions.Skip)]
+public partial class Maui25141 : ContentPage
+{
+    public Maui25141()
+    {
+        InitializeComponent();
+		BindingContext = new Maui25141ViewModel
+		{
+			Text = "Hello, Maui!",
+			TriggerFlag = true
+		};
+    }
+
+    public Maui25141(bool useCompiledXaml)
+    {
+        //this stub will be replaced at compile time
+    }
+
+    [TestFixture]
+    class Test
+    {
+        [SetUp]
+        public void Setup()
+        {
+            Application.SetCurrentApplication(new MockApplication());
+            DispatcherProvider.SetCurrent(new DispatcherProviderStub());
+        }
+
+        [TearDown] public void TearDown()
+        {
+            AppInfo.SetCurrent(null);
+            DeviceInfo.SetCurrent(null);
+        }
+
+        [Test]
+        public void BindingsInDataTriggerAndMultiBindingAreCompiledCorrectly()
+        {
+            MockCompiler.Compile(typeof(Maui25141), treatWarningsAsErrors: true);
+        }
+    }
+}
+
+public class Maui25141ViewModel : INotifyPropertyChanged
+{
+	private bool _triggerFlag;
+	public bool TriggerFlag
+	{
+		get => _triggerFlag;
+		set
+		{
+			_triggerFlag = value;
+			PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(TriggerFlag)));
+		}
+	}
+
+	private string _text;
+	public string Text
+	{
+		get => _text;
+		set
+		{
+			_text = value;
+			PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(Text)));
+		}
+	}
+
+	public event PropertyChangedEventHandler PropertyChanged;
+}