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 ```axaml ``` MainViewModel.cs ```c# public class MainViewModel : ViewModelBase { public AvaloniaList Items { get; } = new(); public HierarchicalTreeDataGridSource Source { get; } public ReactiveCommand Command { get; } public MainViewModel() { Source = new(Items) { Columns = { new HierarchicalExpanderColumn(new TextColumn("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 Chilren { get; } = []; public Item() => N = Random.Shared.Next(10); } ``` MainView.axaml ```xaml ```

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

```c# IEnumerable Children(Visual parent) { foreach (var child in parent.GetVisualChildren()) { if (child is T target) yield return target; foreach (T item in Children(child)) yield return item; } } ```