[C# Markup] ItemsRepeater crashes when used with ItemTemplateSelector

[MartinZikmund]

Discussed in #2404

^{Originally posted by kucint July 1, 2024}
ItemTemplateSelector works fine with ListView, but it crashes with ItemsRepeater:

public sealed partial class MainPage : Page
{
    public MainPage() => this
        .DataContext(new BindableMainPageModel(), (page, vm) => page
        .Background(ThemeResource.Get<Brush>("ApplicationPageBackgroundThemeBrush"))
        .Content(new StackPanel()
        .VerticalAlignment(VerticalAlignment.Center)
        .HorizontalAlignment(HorizontalAlignment.Center)
        .Children(
            new TextBlock()
            .Text("Hello Uno Platform!"),
            //new ListView()                             // ItemTemplateSelector works fine with ListView
            new ItemsRepeater()                          // but it crashes with ItemsRepeater
            .ItemsSource(() => vm.Items)
            .ItemTemplateSelector<Item>((item, selector) => selector
                .Default(() => new TextBlock().Text("def"))
                .Case<ItemA>(itemA => new TextBlock().Text("a"))
                .Case<ItemB>(itemB => new TextBlock().Text("b"))
        )));
}

on net8.0-desktop;
An exception of type 'System.ArgumentException' occurred in Uno.UI.dll but was not handled in user code

on net8.0-windows10.0.19041:
An exception of type 'System.InvalidCastException' occurred in WinRT.Runtime.dll but was not handled in user code

"Uno.Sdk": "5.2.175"

  <PropertyGroup>
    <UnoExtensionsVersion>4.1.24</UnoExtensionsVersion>
    <UnoToolkitVersion>6.0.18</UnoToolkitVersion>
    <UnoThemesVersion>5.0.13</UnoThemesVersion>
    <UnoCSharpMarkupVersion>5.2.14</UnoCSharpMarkupVersion>
  </PropertyGroup>

repro: UnoTemplateSelectorApp.zip

[dansiegel]

@kucint this fix has been merged and should be available in the latest preview version. Please let me know if you have any further issues with this.

Also note that this will be backported to the 5.3 branch and will be in the upcoming 5.3 release.

[kucint]

@kucint this fix has been merged and should be available in the latest preview version. Please let me know if you have any further issues with this.

Also note that this will be backported to the 5.3 branch and will be in the upcoming 5.3 release.

Hi @dansiegel
This fix must be something big, it seems that it fixed as well other issues related to ItemsRepeater I observed from time to time in my app but I could not find any stable repro pattern for them, so I did not report them. Now they all seem to be gone.
BTW, it has been already backported to 5.2, right?

Thanks for this fix, now I have impression that the implementation of ItemsRepeater is becoming stable!
Well done!