From 12b7a5615a29da5cc2d519a78f21f26da96544ff Mon Sep 17 00:00:00 2001
From: Compunet <117437050+dme-compunet@users.noreply.github.com>
Date: Mon, 16 Mar 2026 22:28:19 +0200
Subject: [PATCH] Do not resolve markup extensions when resolving selector
 types (#20903)

* Do not resolve markup extensions when resolving selector types

* Added commen

* Added unit test
---
 .../AvaloniaXamlIlSelectorTransformer.cs      |  4 +++-
 .../Xaml/StyleTests.cs                        | 20 +++++++++++++++++++
 .../Xaml/TestSelectorControl.cs               |  5 +++++
 3 files changed, 28 insertions(+), 1 deletion(-)
 create mode 100644 tests/Avalonia.Markup.Xaml.UnitTests/Xaml/TestSelectorControl.cs

diff --git a/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlSelectorTransformer.cs b/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlSelectorTransformer.cs
index d37cffc360..1a8a80329f 100644
--- a/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlSelectorTransformer.cs
+++ b/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlSelectorTransformer.cs
@@ -209,8 +209,10 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
                 throw new XamlSelectorsTransformException("Unable to parse selector: " + e.Message, node, e);
             }
 
+            // Selectors should resolve control types only.
+            // isMarkupExtension = false to prevent resolving selector types to XExtension.
             var selector = Create(parsed, (p, n) 
-                => TypeReferenceResolver.ResolveType(context, $"{p}:{n}", true, node, true));
+                => TypeReferenceResolver.ResolveType(context, $"{p}:{n}", false, node, true));
             pn.Values[0] = selector;
 
             var templateType = GetLastTemplateTypeFromSelector(selector);
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
index 54f80984ff..95d6cbca94 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
@@ -788,5 +788,25 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
 
             Assert.Equal("Cannot add a Style without selector to a ControlTheme. Line 5, position 14.", exception.Message);
         }
+
+        [Fact]
+        public void Selector_Should_Not_Resolve_To_MarkupExtension_Type()
+        {
+            using var _ = UnitTestApplication.Start(TestServices.StyledWindow);
+
+            var style = (Style)AvaloniaRuntimeXamlLoader.Load(
+                $"""
+                <Style xmlns='https://github.com/avaloniaui'
+                        xmlns:u='using:Avalonia.Markup.Xaml.UnitTests.Xaml'
+                        Selector='u|TestSelectorControl'>
+                </Style>
+                """);
+
+            Assert.NotNull(style.Selector);
+
+            var targetType = style.Selector.TargetType;
+
+            Assert.NotEqual(typeof(TestSelectorControlExtension), targetType);
+        }
     }
 }
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/TestSelectorControl.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/TestSelectorControl.cs
new file mode 100644
index 0000000000..a1cb89c002
--- /dev/null
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/TestSelectorControl.cs
@@ -0,0 +1,5 @@
+namespace Avalonia.Markup.Xaml.UnitTests.Xaml;
+
+public class TestSelectorControl;
+
+public class TestSelectorControlExtension;