From cc1051efa35342ba4ef095b987b3f583cfe550d8 Mon Sep 17 00:00:00 2001
From: Andrey Kunchev <donandren@gmail.com>
Date: Mon, 16 Nov 2020 14:03:13 +0200
Subject: [PATCH 1/2] add failing test for set of base class property

---
 .../Xaml/XamlIlTests.cs                       | 21 ++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/XamlIlTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/XamlIlTests.cs
index 67e46d25c3..77a4932ccc 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/XamlIlTests.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/XamlIlTests.cs
@@ -295,8 +295,27 @@ namespace Avalonia.Markup.Xaml.UnitTests
                 Assert.Equal("Test", templated.Text);
             }
         }
+
+        [Fact]
+        public void Should_Work_With_Base_Property()
+        {
+            var parsed = (ListBox)AvaloniaRuntimeXamlLoader.Load(@"
+<ListBox
+  xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
+  xmlns='https://github.com/avaloniaui'
+  xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests;assembly=Avalonia.Markup.Xaml.UnitTests'
+>
+    <ItemsControl.ItemTemplate>
+      <DataTemplate>
+        <ContentControl Content='{Binding}' />
+      </DataTemplate>
+    </ItemsControl.ItemTemplate>
+</ListBox>");
+
+            Assert.NotNull(parsed.ItemTemplate);
+        }
     }
-    
+
     public class XamlIlBugTestsEventHandlerCodeBehind : Window
     {
         public object SavedContext;

From db96b4d39ee3733dcd55ead409c6df9a7314342f Mon Sep 17 00:00:00 2001
From: Andrey Kunchev <donandren@gmail.com>
Date: Mon, 16 Nov 2020 14:04:09 +0200
Subject: [PATCH 2/2] fix set of base class property in xaml fixes #1926

---
 .../AvaloniaXamlIlTransformInstanceAttachedProperties.cs        | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlTransformInstanceAttachedProperties.cs b/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlTransformInstanceAttachedProperties.cs
index d78ceeb918..f87e73a783 100644
--- a/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlTransformInstanceAttachedProperties.cs
+++ b/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlTransformInstanceAttachedProperties.cs
@@ -22,7 +22,7 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
                 var avaloniaObject = context.Configuration.TypeSystem.FindType("Avalonia.AvaloniaObject");
                 if (avaloniaObject.IsAssignableFrom(targetRef.Type)
                     && avaloniaObject.IsAssignableFrom(declaringRef.Type)
-                    && !targetRef.Type.IsAssignableFrom(declaringRef.Type))
+                    && !declaringRef.Type.IsAssignableFrom(targetRef.Type))
                 {
                     // Instance property
                     var clrProp = declaringRef.Type.GetAllProperties().FirstOrDefault(p => p.Name == prop.Name);