Notifying of a property change when the binding is not direct

[DarioLoll]

Hello, I have a few bindings in my app that are not direct, but instead bind to a property of a property and I just can't get the UI to update even though I am raising the property changed event on all properties.

Here is my exact code:
I am trying to implement a system for having tabs and switching between them, where each tab is a toggle button with an icon and text, and a view to display when the tab is selected.

MainWindowViewModel:

Contains a Tab Manager which contains all the tabs and can switch between them

[ObservableProperty] private TabManagerViewModel _tabManager;

public MainWindowViewModel()
{
    //Vm1 - Vm4 are just examples for different viewmodels for each tab view
    TabManager = new TabManagerViewModel(TabViewModel.ToTab(new Vm1()), TabViewModel.ToTab(new Vm2()),
        TabViewModel.ToTab(new Vm3()), TabViewModel.ToTab(new Vm4()));
    TabManager.Changed += TabManager_Changed;
}

private void TabManager_Changed()
{
    OnPropertyChanged(nameof(TabManager));
}

TabManagerViewModel:

Contains a list of tabs that can be switched between

public event Action? Changed;

public TabManagerViewModel(params TabViewModel[] tabs)
{
    Tabs = new ObservableCollection<TabViewModel>(tabs);
    SelectTab(0.ToString());
}

[ObservableProperty] private ObservableCollection<TabViewModel> _tabs = new();

[ObservableProperty] private TabViewModel _selectedTab;

[RelayCommand]
private void SelectTab(string index)
{
    var newIndex = int.Parse(index);
    var newSelectedTab = Tabs[newIndex];
    if (SelectedTab != newSelectedTab)
    {
        newSelectedTab.IsSelected = true;
        if(SelectedTab != null)
            SelectedTab.IsSelected = false;
        SelectedTab = newSelectedTab;
    }
    else
    {
        SelectedTab.IsSelected = true;
    }
    //As you can see I am trying everything here to get the UI to update
    OnPropertyChanged(nameof(Tabs));
    Tabs.Add(new TabViewModel());
    Tabs.RemoveAt(Tabs.Count - 1);
    foreach (var tab in Tabs)
    {
        tab.NotifyOfChanges();
    }
    Changed?.Invoke();
}

TabViewModel:

 [ObservableProperty] private bool _isSelected;

 //The View model of the window to be displayed when this tab is selected
 public ViewModelBase ViewModel { get; set; }

 public static TabViewModel ToTab(ViewModelBase viewModel)
 {
     return new TabViewModel
     {
         ViewModel = viewModel
     };
 }

 public void NotifyOfChanges()
 {
     OnPropertyChanged(nameof(ViewModel));
     OnPropertyChanged(nameof(IsSelected));
 }

UI in the MainView:

The DataContext here is MainViewModel so I have to go through the TabManager to bind to anything tab related
The ToggleButtons for switching between tabs

<ToggleButton <!-- OtherProperties -->
               IsChecked="{Binding TabManager.Tabs[0].IsSelected}"
						   Command="{Binding TabManager.SelectTabCommand}"
						   CommandParameter="0"/>
<ToggleButton <!-- OtherProperties -->
               IsChecked="{Binding TabManager.Tabs[0].IsSelected}"
						   Command="{Binding TabManager.SelectTabCommand}"
						   CommandParameter="1"/>
<ToggleButton <!-- OtherProperties -->
               IsChecked="{Binding TabManager.Tabs[0].IsSelected}"
						   Command="{Binding TabManager.SelectTabCommand}"
						   CommandParameter="2"/>

The display of the tab window:

<ContentPresenter Grid.Column="2"
				  HorizontalAlignment="Stretch"
				  VerticalAlignment="Stretch"
				  Content="{Binding TabManager.SelectedTab.ViewModel}"/>

I am using the ViewLocator to get the view of the tab from the viewmodel that is the actual value of the content.

So as you can see, I am binding to properties of properties, etc. and the UI won't update even though I call OnPropertyChanged on all of those. Is there a way to fix this, or should bindings like these be avoided.

Also, I do know that there is a built-in TabControl but since I've gone this far, switching over to TabControl is probably going to take more effort than finishing this, I thought.

Sorry for throwing so much code on here, and thanks in advance.

[stevemonaco]

Some advice:

1. Presenters (ie. ContentPresenter) are only valid within ControlTemplates. Use ContentControl instead.
2. Use a TabControl or TabStrip instead of hacking one up like this. You can remove the janky string indexes, too.
3. Double check if you have multiple TabManagers. It's a common beginner mistake to create multiple VMs by accident and update an instance that isn't binded. You can do this by putting a breakpoint in the TagManager's ctor and check if you get multiple calls.

[DarioLoll]

Thank you very much. Simply switching ContentPresenter to ContentControl solved the issue, but yeah, probably should have done my research before. Sorry for bothering