System.InvalidOperationException: The control already has a visual parent.

[mrj001]

Steps:

1. Run the Controls Catalog
2. Choose ComboBox
3. Select an item in the first combo box.
4. Change themes. I switched to Simple - Light.
5. Try to open the first combo box again & it crashes.

here is the stack trace

Unhandled exception. System.InvalidOperationException: The control already has a visual parent.
at Avalonia.Visual.ValidateVisualChild(IVisual c) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Visuals/Visual.cs:line 555
at Avalonia.Visual.<>c.<.ctor>b__16_0(IVisual visual) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Visuals/Visual.cs:line 122
at Avalonia.Collections.AvaloniaList1.InsertRange(Int32 index, IEnumerable1 items) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/Collections/AvaloniaList.cs:line 369
at Avalonia.Controls.Panel.ChildrenChanged(Object sender, NotifyCollectionChangedEventArgs e) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Panel.cs:line 112
at Avalonia.Controls.VirtualizingStackPanel.ChildrenChanged(Object sender, NotifyCollectionChangedEventArgs e) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/VirtualizingStackPanel.cs:line 108
at Avalonia.Collections.AvaloniaList1.NotifyAdd(T item, Int32 index) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/Collections/AvaloniaList.cs:line 662 at Avalonia.Collections.AvaloniaList1.Add(T item) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/Collections/AvaloniaList.cs:line 187
at Avalonia.Controls.Presenters.ItemVirtualizerNone.AddContainers(Int32 index, IEnumerable items) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Presenters/ItemVirtualizerNone.cs:line 96
at Avalonia.Controls.Presenters.ItemVirtualizerNone..ctor(ItemsPresenter owner) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Presenters/ItemVirtualizerNone.cs:line 21
at Avalonia.Controls.Presenters.ItemVirtualizer.Create(ItemsPresenter owner) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Presenters/ItemVirtualizer.cs:line 203
at Avalonia.Controls.Presenters.ItemsPresenter.PanelCreated(IPanel panel) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Presenters/ItemsPresenter.cs:line 151
at Avalonia.Controls.Presenters.ItemsPresenterBase.CreatePanel() in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Presenters/ItemsPresenterBase.cs:line 231
at Avalonia.Controls.Presenters.ItemsPresenterBase.ApplyTemplate() in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Presenters/ItemsPresenterBase.cs:line 137
at Avalonia.Layout.Layoutable.MeasureCore(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/Layoutable.cs:line 554
at Avalonia.Layout.Layoutable.Measure(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/Layoutable.cs:line 364
at Avalonia.Controls.Presenters.ScrollContentPresenter.MeasureOverride(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Presenters/ScrollContentPresenter.cs:line 243
at Avalonia.Layout.Layoutable.MeasureCore(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/Layoutable.cs:line 559
at Avalonia.Layout.Layoutable.Measure(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/Layoutable.cs:line 364
at Avalonia.Controls.Grid.MeasureCell(Int32 cell, Boolean forceInfinityV) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Grid.cs:line 1149
at Avalonia.Controls.Grid.MeasureCellsGroup(Int32 cellsHead, Size referenceSize, Boolean ignoreDesiredSizeU, Boolean forceInfinityV, Boolean& hasDesiredSizeUChanged) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Grid.cs:line 1004
at Avalonia.Controls.Grid.MeasureCellsGroup(Int32 cellsHead, Size referenceSize, Boolean ignoreDesiredSizeU, Boolean forceInfinityV) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Grid.cs:line 968
at Avalonia.Controls.Grid.MeasureOverride(Size constraint) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Grid.cs:line 489
at Avalonia.Layout.Layoutable.MeasureCore(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/Layoutable.cs:line 559
at Avalonia.Layout.Layoutable.Measure(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/Layoutable.cs:line 364
at Avalonia.Layout.Layoutable.MeasureOverride(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/Layoutable.cs:line 625
at Avalonia.Layout.Layoutable.MeasureCore(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/Layoutable.cs:line 559
at Avalonia.Layout.Layoutable.Measure(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/Layoutable.cs:line 364
at Avalonia.Layout.LayoutHelper.MeasureChild(ILayoutable control, Size availableSize, Thickness padding) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/LayoutHelper.cs:line 40
at Avalonia.Layout.LayoutHelper.MeasureChild(ILayoutable control, Size availableSize, Thickness padding, Thickness borderThickness) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/LayoutHelper.cs:line 33
at Avalonia.Controls.Border.MeasureOverride(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Border.cs:line 121
at Avalonia.Layout.Layoutable.MeasureCore(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/Layoutable.cs:line 559
at Avalonia.Layout.Layoutable.Measure(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/Layoutable.cs:line 364
at Avalonia.Layout.LayoutHelper.MeasureChild(ILayoutable control, Size availableSize, Thickness padding) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/LayoutHelper.cs:line 40
at Avalonia.Layout.LayoutHelper.MeasureChild(ILayoutable control, Size availableSize, Thickness padding, Thickness borderThickness) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/LayoutHelper.cs:line 33
at Avalonia.Controls.Presenters.ContentPresenter.MeasureOverride(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Presenters/ContentPresenter.cs:line 339
at Avalonia.Layout.Layoutable.MeasureCore(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/Layoutable.cs:line 559
at Avalonia.Layout.Layoutable.Measure(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/Layoutable.cs:line 364
at Avalonia.Layout.LayoutHelper.MeasureChild(ILayoutable control, Size availableSize, Thickness padding) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/LayoutHelper.cs:line 40
at Avalonia.Controls.Decorator.MeasureOverride(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Decorator.cs:line 54
at Avalonia.Controls.Primitives.VisualLayerManager.MeasureOverride(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Primitives/VisualLayerManager.cs:line 136
at Avalonia.Layout.Layoutable.MeasureCore(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/Layoutable.cs:line 559
at Avalonia.Layout.Layoutable.Measure(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/Layoutable.cs:line 364
at Avalonia.Layout.Layoutable.MeasureOverride(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/Layoutable.cs:line 625
at Avalonia.Layout.Layoutable.MeasureCore(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/Layoutable.cs:line 559
at Avalonia.Layout.Layoutable.Measure(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/Layoutable.cs:line 364
at Avalonia.Layout.Layoutable.MeasureOverride(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/Layoutable.cs:line 625
at Avalonia.Controls.Primitives.PopupRoot.MeasureOverride(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Primitives/PopupRoot.cs:line 137
at Avalonia.Controls.WindowBase.MeasureCore(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/WindowBase.cs:line 246
at Avalonia.Layout.Layoutable.Measure(Size availableSize) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/Layoutable.cs:line 364
at Avalonia.Layout.LayoutManager.Measure(ILayoutable control) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/LayoutManager.cs:line 287
at Avalonia.Layout.LayoutManager.ExecuteInitialLayoutPass() in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Layout/LayoutManager.cs:line 174
at Avalonia.Controls.WindowBase.Show() in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/WindowBase.cs:line 162
at Avalonia.Controls.Primitives.Popup.Open() in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Primitives/Popup.cs:line 473
at Avalonia.Controls.Primitives.Popup.IsOpenChanged(AvaloniaPropertyChangedEventArgs1 e) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Primitives/Popup.cs:line 541 at Avalonia.Controls.Primitives.Popup.<>c.<.cctor>b__22_1(Popup x, AvaloniaPropertyChangedEventArgs e) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Primitives/Popup.cs:line 144 at Avalonia.AvaloniaObjectExtensions.<>c__DisplayClass23_01.b__0(AvaloniaPropertyChangedEventArgs e) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/AvaloniaObjectExtensions.cs:line 583
at System.Reactive.Subjects.Subject1.OnNext(T value) in /_/Rx.NET/Source/src/System.Reactive/Subjects/Subject.cs:line 148 at Avalonia.AvaloniaProperty1.NotifyChanged(AvaloniaPropertyChangedEventArgs1 e) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/AvaloniaProperty1.cs:line 80
at Avalonia.AvaloniaObject.RaisePropertyChanged[T](AvaloniaPropertyChangedEventArgs1 change) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/AvaloniaObject.cs:line 719 at Avalonia.AvaloniaObject.RaisePropertyChanged[T](AvaloniaProperty1 property, Optional1 oldValue, BindingValue1 newValue, BindingPriority priority) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/AvaloniaObject.cs:line 632
at Avalonia.AvaloniaObject.SetAndRaise[T](AvaloniaProperty1 property, T& field, T value) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/AvaloniaObject.cs:line 662 at Avalonia.Controls.Primitives.Popup.set_IsOpen(Boolean value) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Primitives/Popup.cs:line 206 at Avalonia.Controls.Primitives.Popup.<>c.<.cctor>b__22_3(Popup o, Boolean v) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Primitives/Popup.cs:line 38 at Avalonia.DirectProperty2.InvokeSetter(IAvaloniaObject instance, BindingValue1 value) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/DirectProperty.cs:line 172 at Avalonia.AvaloniaObject.SetDirectValueUnchecked[T](DirectPropertyBase1 property, BindingValue1 value) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/AvaloniaObject.cs:line 797 at Avalonia.AvaloniaObject.DirectBindingSubscription1.OnNext(BindingValue1 value) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/AvaloniaObject.cs:line 888 at Avalonia.Reactive.SingleSubscriberObservableBase1.PublishNext(T value) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/Reactive/SingleSubscriberObservableBase.cs:line 49
at Avalonia.Reactive.TypedBindingAdapter1.OnNext(BindingValue1 value) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/Reactive/TypedBindingAdapter.cs:line 31
at Avalonia.Reactive.SingleSubscriberObservableBase1.PublishNext(T value) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/Reactive/SingleSubscriberObservableBase.cs:line 49 at Avalonia.Reactive.BindingValueAdapter1.OnNext(T value) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/Reactive/BindingValueAdapter.cs:line 18
at Avalonia.Reactive.SingleSubscriberObservableBase1.PublishNext(T value) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/Reactive/SingleSubscriberObservableBase.cs:line 49 at Avalonia.Data.TemplateBinding.PublishValue() in /Users/mj/Documents/develop/avalonia/Avalonia/src/Markup/Avalonia.Markup/Data/TemplateBinding.cs:line 145 at Avalonia.Data.TemplateBinding.TemplatedParentPropertyChanged(Object sender, AvaloniaPropertyChangedEventArgs e) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Markup/Avalonia.Markup/Data/TemplateBinding.cs:line 183 at Avalonia.AvaloniaObject.RaisePropertyChanged[T](AvaloniaPropertyChangedEventArgs1 change) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/AvaloniaObject.cs:line 720
at Avalonia.AvaloniaObject.RaisePropertyChanged[T](AvaloniaProperty1 property, Optional1 oldValue, BindingValue1 newValue, BindingPriority priority) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/AvaloniaObject.cs:line 632 at Avalonia.AvaloniaObject.SetAndRaise[T](AvaloniaProperty1 property, T& field, T value) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/AvaloniaObject.cs:line 662
at Avalonia.Controls.ComboBox.set_IsDropDownOpen(Boolean value) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/ComboBox.cs:line 101
at Avalonia.Controls.ComboBox.<>c.<.cctor>b__13_4(ComboBox o, Boolean v) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/ComboBox.cs:line 35
at Avalonia.DirectProperty2.InvokeSetter(IAvaloniaObject instance, BindingValue1 value) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/DirectProperty.cs:line 172
at Avalonia.AvaloniaObject.SetDirectValueUnchecked[T](DirectPropertyBase1 property, T value) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/AvaloniaObject.cs:line 764 at Avalonia.AvaloniaObject.SetValue[T](DirectPropertyBase1 property, T value) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/AvaloniaObject.cs:line 367
at Avalonia.DirectPropertyBase1.RouteSetValue(IAvaloniaObject o, Object value, BindingPriority priority) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/DirectPropertyBase.cs:line 158 at Avalonia.AvaloniaObjectExtensions.SetValue(IAvaloniaObject target, AvaloniaProperty property, Object value, BindingPriority priority) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/AvaloniaObjectExtensions.cs:line 529 at Avalonia.Data.TemplateBinding.System.IObserver<System.Object>.OnNext(Object value) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Markup/Avalonia.Markup/Data/TemplateBinding.cs:line 109 at Avalonia.Reactive.LightweightObservableBase1.PublishNext(T value) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/Reactive/LightweightObservableBase.cs:line 138
at Avalonia.Reactive.AvaloniaPropertyObservable1.PropertyChanged(Object sender, AvaloniaPropertyChangedEventArgs e) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/Reactive/AvaloniaPropertyObservable.cs:line 61 at Avalonia.AvaloniaObject.RaisePropertyChanged[T](AvaloniaPropertyChangedEventArgs1 change) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/AvaloniaObject.cs:line 720
at Avalonia.AvaloniaObject.RaisePropertyChanged[T](AvaloniaProperty1 property, Optional1 oldValue, BindingValue1 newValue, BindingPriority priority) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/AvaloniaObject.cs:line 632 at Avalonia.AvaloniaObject.SetAndRaise[T](AvaloniaProperty1 property, T& field, T value) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/AvaloniaObject.cs:line 662
at Avalonia.Controls.Primitives.ToggleButton.set_IsChecked(Nullable1 value) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Primitives/ToggleButton.cs:line 96 at Avalonia.Controls.Primitives.ToggleButton.Toggle() in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Primitives/ToggleButton.cs:line 136 at Avalonia.Controls.Primitives.ToggleButton.OnClick() in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Primitives/ToggleButton.cs:line 112 at Avalonia.Controls.Button.OnPointerPressed(PointerPressedEventArgs e) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/Button.cs:line 290 at Avalonia.Input.InputElement.<>c.<.cctor>b__26_8(InputElement x, PointerPressedEventArgs e) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Input/InputElement.cs:line 182 at Avalonia.Interactivity.RoutedEvent1.<>c__DisplayClass2_01.<AddClassHandler>g__Adapter|0(Object sender, RoutedEventArgs e) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Interactivity/RoutedEvent.cs:line 143 at Avalonia.Interactivity.RoutedEvent.<>c__DisplayClass23_0.<AddClassHandler>b__0(ValueTuple2 args) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Interactivity/RoutedEvent.cs:line 92
at System.Reactive.Subjects.Subject`1.OnNext(T value) in /_/Rx.NET/Source/src/System.Reactive/Subjects/Subject.cs:line 148
at Avalonia.Interactivity.RoutedEvent.InvokeRaised(Object sender, RoutedEventArgs e) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Interactivity/RoutedEvent.cs:line 99
at Avalonia.Interactivity.EventRoute.RaiseEventImpl(RoutedEventArgs e) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Interactivity/EventRoute.cs:line 148
at Avalonia.Interactivity.EventRoute.RaiseEvent(IInteractive source, RoutedEventArgs e) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Interactivity/EventRoute.cs:line 101
at Avalonia.Interactivity.Interactive.RaiseEvent(RoutedEventArgs e) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Interactivity/Interactive.cs:line 120
at Avalonia.Input.MouseDevice.MouseDown(IMouseDevice device, UInt64 timestamp, IInputElement root, Point p, PointerPointProperties properties, KeyModifiers inputModifiers) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Input/MouseDevice.cs:line 242
at Avalonia.Input.MouseDevice.ProcessRawEvent(RawPointerEventArgs e) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Input/MouseDevice.cs:line 151
at Avalonia.Input.MouseDevice.ProcessRawEvent(RawInputEventArgs e) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Input/MouseDevice.cs:line 84
at Avalonia.Input.InputManager.ProcessInput(RawInputEventArgs e) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Input/InputManager.cs:line 35
at Avalonia.Controls.TopLevel.HandleInput(RawInputEventArgs e) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/TopLevel.cs:line 473
at Avalonia.Native.WindowBaseImpl.RawMouseEvent(AvnRawMouseEventType type, UInt32 timeStamp, AvnInputModifiers modifiers, AvnPoint point, AvnVector delta) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Native/WindowImplBase.cs:line 294
at Avalonia.Native.WindowBaseImpl.WindowBaseEvents.Avalonia.Native.Interop.IAvnWindowBaseEvents.RawMouseEvent(AvnRawMouseEventType type, UInt32 timeStamp, AvnInputModifiers modifiers, AvnPoint point, AvnVector delta) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Native/WindowImplBase.cs:line 192
at Avalonia.Native.Interop.IAvnWindowBaseEventsShadow.IAvnWindowBaseEventsVtbl.RawMouseEvent(IntPtr thisObject, Int32 param0, UInt32 param1, Int32 param2, AvnPoint param3, AvnVector param4) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Native/Generated/Interfaces.cs:line 2834
--- End of stack trace from previous location where exception was thrown ---
at Avalonia.Native.PlatformThreadingInterface.RunLoop(CancellationToken cancellationToken) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Native/PlatformThreadingInterface.cs:line 91
at Avalonia.Threading.Dispatcher.MainLoop(CancellationToken cancellationToken) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Base/Threading/Dispatcher.cs:line 61
at Avalonia.Controls.ApplicationLifetimes.ClassicDesktopStyleApplicationLifetime.Start(String[] args) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/ApplicationLifetimes/ClassicDesktopStyleApplicationLifetime.cs:line 107
at Avalonia.ClassicDesktopStyleApplicationLifetimeExtensions.StartWithClassicDesktopLifetime[T](T builder, String[] args, ShutdownMode shutdownMode) in /Users/mj/Documents/develop/avalonia/Avalonia/src/Avalonia.Controls/ApplicationLifetimes/ClassicDesktopStyleApplicationLifetime.cs:line 134
at ControlCatalog.NetCore.Program.Main(String[] args) in /Users/mj/Documents/develop/avalonia/Avalonia/samples/ControlCatalog.NetCore/Program.cs:line 102

This is the output of "dotnet --info"

.NET Core SDK (reflecting any global.json):
Version: 3.1.401
Commit: 39d17847db

Runtime Environment:
OS Name: Mac OS X
OS Version: 10.15
OS Platform: Darwin
RID: osx.10.15-x64
Base Path: /usr/local/share/dotnet/sdk/3.1.401/

Host (useful for support):
Version: 3.1.8
Commit: 9c1330dedd

.NET Core SDKs installed:
3.1.201 [/usr/local/share/dotnet/sdk]
3.1.302 [/usr/local/share/dotnet/sdk]
3.1.401 [/usr/local/share/dotnet/sdk]
3.1.402 [/usr/local/share/dotnet/sdk]

.NET Core runtimes installed:
Microsoft.AspNetCore.App 3.1.7 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.8 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 2.1.22 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 2.2.8 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.7 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.8 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]

To install additional .NET Core runtimes or SDKs:
https://aka.ms/dotnet-download

version: HEAD is at 129dfda

[FoggyFinder]

Probably duplicate of #4265

[mrj001]

I saw that one, but I didn't think it would be a duplicate because the stack traces are different, and this one is a ComboBox instead of a ListBox.

[FoggyFinder]

Yeah, that's why I wrote "Probably"

[HendrikMennen]

I have a similar error with ContextMenu's sometimes

[grokys]

Should be long fixed by now ;)