Access to the parent MVVM model from the collection

Question

The figure above shows my program. Arrows indicate Binding.

My MainWindow.xaml has its data set located as MainVM.

The window has a tab control bound to ObservableCollectionfrom ViewModels. Using a data template, the tab control displays the corresponding views ViewModel.

ObservableCollectionlocated in MainVM.

How to access the properties found in MainVMfrom ViewModel(enclosed in an ObservableCollection)?

I am open to answers requiring modifications to my programming model.

Answer 1

, .,.

ViewModel MainVM. , , ViewModel, , . SOLID, .

, MainVM ViewModel, ViewModel. , .

overkill ( ), , MainVM this . :.

public class ViewModel
{
    private readonly MainVM _parent;

    public MainVM Parent => _parent;

    public ViewModel(MainVM parent)
    {
          _parent = parent;
    }
 }

ViewModel :

 ViewModel vm = new ViewModel(this);

Answer 2

, , , ViewModel MainVM ViewModel.

- ViewModel (, , MainVM -?), MainVM MainVM ViewModel.

Answer 3

ViewModel? MainVM ViewModel , , ViewModel MainVM .

, ViewModel MainVM. ( ).