[Bug] ComboBox throws "The control already has a visual parent" error when it's pressed

[PieroCastillo]

Describe the bug
I tried to make a ThemeChanger (like

Avalonia/samples/ControlCatalog/MainView.xaml

Lines 80 to 85 in b6ccad0

	<ComboBox x:Name="Themes" SelectedIndex="0">
	<ComboBoxItem>Fluent - Light</ComboBoxItem>
	<ComboBoxItem>Fluent - Dark</ComboBoxItem>
	<ComboBoxItem>Simple - Light</ComboBoxItem>
	<ComboBoxItem>Simple - Dark</ComboBoxItem>
	</ComboBox>

) but when I press throws an error.

To Reproduce
I don't know exactly the causes, so, I'm going to put the code:
App.xaml.cs
MainWindow.xaml
MainWindow.xaml.cs

Expected behavior
Error when the ComboBox is pressed.

Screenshots

Normal App

2021-02-07.22-43-08.mp4

App without custom controls

2021-02-07.22-53-39.mp4

Desktop (please complete the following information):

• OS: Windows 10 20H2
• Version : Avalonia 0.10.0 stable

[FoggyFinder]

Duplicate of #4839

[maxkatz6]

Duplicate of #4839
But with some additional context

[maxkatz6]

@PieroCastillo long story short, the problem is with reusing same combobox items when its template was changed with new children list container.
As a workaround, if you replace your items with binding to Items property and use item template for items, it should be solved.

IIRC problem makes sense only with updating list control template while its open and items can't be reused.

[PieroCastillo]

@maxkatz6 THANKSSSSSSSSSSS :DDDDDDDDDDDD
With this code is enough:

 <ComboBox SelectedIndex="0"
                VirtualizationMode="None"
                SelectionChanged="ChangeTheme">
     <ComboBox.ItemTemplate>
         <DataTemplate>
            <TextBlock Text="{Binding .}"/>
         </DataTemplate> 
     </ComboBox.ItemTemplate>
    <l:ArrayList>
         <sys:String>Fluent Light</sys:String>
        <sys:String>Fluent Dark</sys:String>
   </l:ArrayList>
</ComboBox>

[PieroCastillo]

now all that remains is to improve the performance of the style system. ;)