The items are not sorted after setting column SortDirection, despite the column header shows arrow.

[sinatrocious]

Describe the bug

I am setting column SortDirection in code, but the sorting is not happening. Sorting seems to only works if I click column header.

To Reproduce

1. Create new avalonia desktop application.
2. Add Avalonia.Controls.TreeDataGrid nuget.
3. Do following changes :

Repro

App.axaml

    <Application.Styles>
        <FluentTheme />
        <StyleInclude Source="avares://Avalonia.Controls.TreeDataGrid/Themes/Fluent.axaml"/>
    </Application.Styles>

MainViewModel.cs

public class MainViewModel : ViewModelBase
{
    public AvaloniaList<Item> Items { get; } = new();
    public HierarchicalTreeDataGridSource<Item> Source { get; }

    public ReactiveCommand<Unit, Unit> Command { get; }

    public MainViewModel()
    {
        Source = new(Items)
        {
            Columns =
            {
                new HierarchicalExpanderColumn<Item>(new TextColumn<Item, int>("N", o => o.N), o => o.Chilren)
                {
                    SortDirection = ListSortDirection.Ascending
                }
            }
        };

        Command = ReactiveCommand.Create(() => Items.Add(new()));
    }
}

public class Item
{
    public int N { get; }
    public AvaloniaList<Item> Chilren { get; } = [];

    public Item() => N = Random.Shared.Next(10);
}

MainView.axaml

    <Grid>
        <TreeDataGrid Source="{Binding Source}"/>
        <Button Content="Add"
                Command="{Binding Command}"/>
    </Grid>

4. Run, click button several time and observe issue:

Expected behavior

I expect sorting to work according to SortDirection.

Environment

• OS: Windows 11
• Avalonia-Version: 11.0.10
• TreeDataGrid-Version: 11.0.2

Additional context

I've tried to set SortDirection after 5s delay after window is shown. The column header will show arrow, but no sorting occurs. I guess this public property is used internally to toggle displaying of arrow, but then how do I force sorting?

I guess simulating mouse click on column header is a workaround, but after quick research I am unable to find anything what can help me to build such workaround.

[sinatrocious]

Possible workaround is to send click event to first column:

var firstColumn = Children<TreeDataGridColumnHeader>(treeDataGrid).First();
firstColumn.RaiseEvent(new RoutedEventArgs { RoutedEvent = Button.ClickEvent });

Children method

IEnumerable<T> Children<T>(Visual parent)
{
    foreach (var child in parent.GetVisualChildren())
    {
        if (child is T target)
            yield return target;

        foreach (T item in Children<T>(child))
            yield return item;
    }
}