Accept base TargetType in ItemContainerTheme

src/Avalonia.Controls/ItemsControl.cs

@@ -667,7 +667,7 @@ namespace Avalonia.Controls
 
             if (itemContainerTheme is null)
                 container.Theme = null;
-            else if (GetStyleKey(container) == itemContainerTheme.TargetType)
+            else if (itemContainerTheme.TargetType?.IsAssignableFrom(GetStyleKey(container)) == true)
                 container.Theme = itemContainerTheme;
 
             if (item is not Control)

tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs

@@ -129,6 +129,20 @@ namespace Avalonia.Controls.UnitTests
             Assert.Same(container.Theme, theme);
         }
 
+        [Fact]
+        public void Container_Should_Have_Theme_Set_To_ItemContainerTheme_With_Base_TargetType()
+        {
+            using var app = Start();
+            var theme = new ControlTheme { TargetType = typeof(Control) };
+            var target = CreateTarget(
+                itemsSource: new[] { "Foo" },
+                itemContainerTheme: theme);
+
+            var container = GetContainer(target);
+
+            Assert.Same(container.Theme, theme);
+        }
+
         [Fact]
         public void ItemContainerTheme_Can_Be_Changed()
         {