fix(xBind): Fix xBind to other control without code-behind base class

src/Uno.UI.Tests/Windows_UI_Xaml_Data/xBindTests/Controls/xBind_UserControl_To_OtherControl.xaml

@@ -0,0 +1,14 @@
+<UserControl
+    x:Class="Uno.UI.Tests.Windows_UI_Xaml_Data.xBindTests.Controls.xBind_UserControl_To_OtherControl"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:local="using:Uno.UI.Tests.Windows_UI_Xaml_Data.xBindTests.Controls"
+    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">
+
+	<local:xBind_UserControl_To_OtherControl_Inner
+		MyProperty="{x:Bind MyProperty, Mode=OneWay}" />
+</UserControl>

src/Uno.UI.Tests/Windows_UI_Xaml_Data/xBindTests/Controls/xBind_UserControl_To_OtherControl.xaml.cs

@@ -0,0 +1,40 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using System.IO;
+using System.Linq;
+using System.Runtime.InteropServices.WindowsRuntime;
+using Windows.Foundation;
+using Windows.Foundation.Collections;
+using Windows.UI.Xaml;
+using Windows.UI.Xaml.Controls;
+using Windows.UI.Xaml.Controls.Primitives;
+using Windows.UI.Xaml.Data;
+using Windows.UI.Xaml.Input;
+using Windows.UI.Xaml.Media;
+using Windows.UI.Xaml.Navigation;
+
+// The User Control item template is documented at https://go.microsoft.com/fwlink/?LinkId=234236
+
+namespace Uno.UI.Tests.Windows_UI_Xaml_Data.xBindTests.Controls
+{
+	#pragma warning disable UXAML0002
+	public sealed partial class xBind_UserControl_To_OtherControl /* : UserControl: Don't specify the base type so x:Bind generator lookups uses the XAML control type */
+#pragma warning restore UXAML0002
+	{
+		public xBind_UserControl_To_OtherControl()
+		{
+			this.InitializeComponent();
+		}
+
+		public string MyProperty
+		{
+			get { return (string)GetValue(MyPropertyProperty); }
+			set { SetValue(MyPropertyProperty, value); }
+		}
+
+		// Using a DependencyProperty as the backing store for MyProperty.  This enables animation, styling, binding, etc...
+		public static readonly DependencyProperty MyPropertyProperty =
+			DependencyProperty.Register("MyProperty", typeof(string), typeof(xBind_UserControl_To_OtherControl), new PropertyMetadata("Default string"));
+	}
+}

src/Uno.UI.Tests/Windows_UI_Xaml_Data/xBindTests/Controls/xBind_UserControl_To_OtherControl_Inner.xaml

@@ -0,0 +1,15 @@
+<UserControl
+    x:Class="Uno.UI.Tests.Windows_UI_Xaml_Data.xBindTests.Controls.xBind_UserControl_To_OtherControl_Inner"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:local="using:Uno.UI.Tests.Windows_UI_Xaml_Data.xBindTests.Controls"
+    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 x:Name="tb1" x:FieldModifier="public" Text="{x:Bind MyProperty, Mode=OneWay}" />
+	</Grid>
+</UserControl>

src/Uno.UI.Tests/Windows_UI_Xaml_Data/xBindTests/Controls/xBind_UserControl_To_OtherControl_Inner.xaml.cs

@@ -0,0 +1,40 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using System.IO;
+using System.Linq;
+using System.Runtime.InteropServices.WindowsRuntime;
+using Windows.Foundation;
+using Windows.Foundation.Collections;
+using Windows.UI.Xaml;
+using Windows.UI.Xaml.Controls;
+using Windows.UI.Xaml.Controls.Primitives;
+using Windows.UI.Xaml.Data;
+using Windows.UI.Xaml.Input;
+using Windows.UI.Xaml.Media;
+using Windows.UI.Xaml.Navigation;
+
+// The User Control item template is documented at https://go.microsoft.com/fwlink/?LinkId=234236
+
+namespace Uno.UI.Tests.Windows_UI_Xaml_Data.xBindTests.Controls
+{
+	#pragma warning disable UXAML0002
+	public sealed partial class xBind_UserControl_To_OtherControl_Inner /* : UserControl: Don't specify the base type so x:Bind generator lookups uses the XAML control type */
+#pragma warning restore UXAML0002
+	{
+		public xBind_UserControl_To_OtherControl_Inner()
+		{
+			this.InitializeComponent();
+		}
+
+		public string MyProperty
+		{
+			get { return (string)GetValue(MyPropertyProperty); }
+			set { SetValue(MyPropertyProperty, value); }
+		}
+
+		// Using a DependencyProperty as the backing store for MyProperty.  This enables animation, styling, binding, etc...
+		public static readonly DependencyProperty MyPropertyProperty =
+			DependencyProperty.Register("MyProperty", typeof(string), typeof(xBind_UserControl_To_OtherControl_Inner), new PropertyMetadata("Default string"));
+	}
+}

src/Uno.UI.Tests/Windows_UI_Xaml_Data/xBindTests/Given_xBind_UserControl.cs

@@ -23,5 +23,25 @@ public void When_Initial_Value()
 
 			Assert.AreEqual("Default string", _MyProperty.Text);
 		}
+
+		[TestMethod]
+		public void When_xBind_UserControl_To_OtherControl()
+		{
+			var SUT = new xBind_UserControl_To_OtherControl();
+
+			var tb1 = SUT.FindName("tb1") as TextBlock;
+			Assert.IsNotNull(tb1);
+			Assert.AreEqual("", tb1.Text);
+
+			SUT.ForceLoaded();
+
+			Assert.AreEqual("Default string", tb1.Text);
+
+			var inner = SUT.Content as xBind_UserControl_To_OtherControl_Inner;
+
+			Assert.IsNotNull(inner);
+			Assert.AreEqual("Default string", inner.MyProperty);
+			Assert.AreEqual("Default string", tb1.Text);
+		}
 	}
 }

src/Uno.UI/UI/Xaml/Data/BindingHelper.cs

@@ -1,6 +1,7 @@
 #nullable enable
 using System;
 using System.Collections.Generic;
+using System.Runtime.CompilerServices;
 using System.Text;
 using Windows.UI.Xaml;
 using Windows.UI.Xaml.Data;
@@ -9,18 +10,26 @@ namespace Uno.UI.Xaml
 {
 	public static class BindingHelper
 	{
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
 		public static Binding SetBindingXBindProvider(Binding binding, object compiledSource, Func<object, object> xBindSelector, string[]? propertyPaths = null)
 			=> SetBindingXBindProvider(binding, compiledSource, xBindSelector, null, propertyPaths);
 
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
 		public static Binding SetBindingXBindProvider(Binding binding, object compiledSource, Func<object, object> xBindSelector, Action<object, object>? xBindBack, string[]? propertyPaths = null)
 		{
 			binding.SetBindingXBindProvider(compiledSource, xBindSelector, xBindBack, propertyPaths);
 			return binding;
 		}
 
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
 		public static AttachedDependencyObject GetDependencyObjectForXBind(this object instance)
 			=> DependencyObjectExtensions.GetAttachedDependencyObject(instance);
 
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
+		public static DependencyObject GetDependencyObjectForXBind(this DependencyObject instance)
+			=> instance;
+
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
 		public static void ApplyXBind(this DependencyObject instance)
 			=> (instance as IDependencyObjectStoreProvider)?.Store.ApplyCompiledBindings();