Avalonia (как сделать активной определенную вкладку)

private int _selectedTabIndex;
public int SelectedTabIndex
{
get => _selectedTabIndex;
set => this.RaiseAndSetIfChanged(ref _selectedTabIndex, value);
}

public ReactiveCommand<Unit, Unit> DoTheThing { get; }
 
public MainWindowViewModel()
{
DoTheThing = ReactiveCommand.Create(RunTheThing);
}
 
void RunTheThing()
{
SelectedTabIndex = 1;
}

public class FirstViewModel
{
    ReactiveCommand ClickCommand { get; set; }
}

public class SecondViewModel
{
    ReactiveCommand ClickCommand { get; set; }
}

    public class Tab1ViewModel
    {
        public TabChangingEventArgs TabChanging;
        public ReactiveCommand<Unit, Unit> DoTheThing { get; }
        public Tab1ViewModel() => DoTheThing = ReactiveCommand.Create(() => TabChanging?.Invoke(this, 1));
    }

    public class MainWindowViewModel : ReactiveObject
    {
        public ObservableCollection<TabItem> Tabs { get; set; } = new ObservableCollection<TabItem>();
 
        private int _selectedTabIndex;
        public int SelectedTabIndex
        {
            get => _selectedTabIndex;
            set => this.RaiseAndSetIfChanged(ref _selectedTabIndex, value);
        }
 
        public MainWindowViewModel()
        {
            var tab1 = new Tab1ViewModel();
            var tab2 = new Tab2ViewModel();
 
            tab1.TabChanging += OnTabChanging;
            tab2.TabChanging += OnTabChanging;
 
            Tabs.Add(new TabItem() { Content = new Tab1UserControl() { DataContext = tab1 }, Header = "Tab 1" });
            Tabs.Add(new TabItem() { Content = new Tab2UserControl() { DataContext = tab2 }, Header = "Tab 2" });
        }
 
        private void OnTabChanging(object sender, int index) => SelectedTabIndex = index;
    }

<Window x:Class="AvaloniaApplication1.Views.MainWindow" xmlns="https://github.com/avaloniaui" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" >
 
    <TabControl SelectedIndex="{Binding SelectedTabIndex}" Items="{Binding Tabs}"/>
    
</Window>

public class Model 
{
    public int Result { get; set; } = 0;
}