fix: fix container selection state issue.

src/Ursa/Controls/ComboBox/MultiComboBoxItem.cs

@@ -13,6 +13,7 @@ public class MultiComboBoxItem: ContentControl
     private MultiComboBox? _parent;
     private static readonly Point s_invalidPoint = new (double.NaN, double.NaN);
     private Point _pointerDownPoint = s_invalidPoint;
+    private bool _updateInternal;
     
     public static readonly StyledProperty<bool> IsSelectedProperty = AvaloniaProperty.Register<MultiComboBoxItem, bool>(
         nameof(IsSelected));
@@ -34,6 +35,7 @@ public class MultiComboBoxItem: ContentControl
 
     private void OnSelectionChanged(AvaloniaPropertyChangedEventArgs<bool> args)
     {
+        if (_updateInternal) return;
         var parent = this.FindLogicalAncestorOfType<MultiComboBox>();
         if (args.NewValue.Value)
         {
@@ -94,4 +96,15 @@ public class MultiComboBoxItem: ContentControl
             }
         }
     }
+
+    protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
+    {
+        base.OnAttachedToVisualTree(e);
+        _updateInternal = true;
+        if (_parent?.ItemsPanelRoot is VirtualizingPanel)
+        {
+            IsSelected =  _parent?.SelectedItems?.Contains(DataContext) ?? false;
+        }
+        _updateInternal = false;
+    }
 }