WPF ObservableCollection and menuItems

Question

On the base of this sample, I'd like to Add, Remove items from Menu programmatically, for example in this way:

    void ChangeItemSubitems()
    {
        // TODO: Add event handler implementation here.
        MenuItems.Add(new MenuItemViewModel { Header = "delta" });
        MenuItems[3].MenuItems = new ObservableCollection<MenuItemViewModel>();
        MenuItems[3].MenuItems.Add(new MenuItemViewModel { Header = "delta 1" });
        MenuItems[3].MenuItems.Add(new MenuItemViewModel { Header = "delta 2" });
        MenuItems.Remove(MenuItems[1].MenuItems[0]);
    }

Only the Add of Items at high level works fine, not submenu, neither the Remove. What is it wrong? Could you give me some hints? Thanks

EDIT: change made to MenuItemViewModel

    public class MenuItemViewModel : ViewModelBase 
{
    private readonly ICommand _command;

    public MenuItemViewModel()
    {
        _command = new CommandViewModel(Execute);
    }

    public MenuItemViewModel(Action action)
    {
        _command = new CommandViewModel(action);
    }

    private string _header;

    public string Header 
    { 
      get { return _header;  }
      set
      {
            _header = value;
            RaisePropertyChangedEvent("Header");
      }
    }

    public ObservableCollection<MenuItemViewModel> MenuItems { get; set; }

    public ICommand Command
    {
        get
        {
            return _command;
        }
    }

    private void Execute()
    {
        // (NOTE: In a view model, you normally should not use MessageBox.Show()).
        MessageBox.Show("Clicked at " + Header);
    }
}

public class ViewModelBase : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    protected void RaisePropertyChangedEvent(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChangedEventArgs e = new PropertyChangedEventArgs(propertyName);
            PropertyChanged(this, e);
        }
    }
}

Answer 1

Your problem is most probably with

public ObservableCollection<MenuItemViewModel> MenuItems { get; set; }

While ObservableCollection will notify the UI when there are item changes, your MenuItemViewModel still needs to notify when the collection itself changes. So try

private ObservableCollection<MenuItemViewModel> _menuItems;
public ObservableCollection<MenuItemViewModel> MenuItems
{
    get
    {
        return _menuItems;
    }
    set
    {
        _menuItems = value;
        RaisePropertyChangedEvent("MenuItems");
    }
}

Edit. The remove statement has a different problem:

MenuItems.Remove(MenuItems[1].MenuItems[0]);

This tries to remove the inner submenu-item from an outer collection. However, MenuItems[1].MenuItems[0] is not an element of MenuItems to begin with, so Remove should return false in this case and WPF is certainly not at fault for not changing the view.

Try the following instead:

MenuItems[1].MenuItems.Remove(MenuItems[1].MenuItems[0]);

It should find and remove the specified item.