Conversion between nested ViewModel and Data Transfer Object

Conversion is for nested ViewModels is possible. Your DTO must use a property type that inherits IList and has a parameterless constructor.

// C# code of DTO class
public class NestedTransferDataObject
{
    public string Name { get; set; }

    public List<NestedTransferDataObject> Others { get; set; }
}

The ViewModel property type must be (or derived from) ObservableViewModelCollection<>.

// C# code of your ViewModel class
[Dto(typeof(NestedTransferDataObject))]
public class NestedViewModel : ViewModel
{
    private string _name;

    [DtoProperty]
    public string Name
    {
        get => _name;
        set => SetProperty(ref _name, value);
    }

    [DtoProperty]
    public ObservableViewModelCollection<NestedViewModel> Others { get; }

    public NestedViewModel()
    {
        Others = new ObservableViewModelCollection<NestedViewModel>(this);
    }
}

If those requirements are met, you can execute the following conversion just fine:

// C# code of the conversion
var dto = new NestedTransferDataObject
{
    Name = "Timmy",
    Others = new List<NestedTransferDataObject>(new[] {
        new NestedTransferDataObject { PersonName = "Bobby" }
    })
};
var viewModel = dto.ToViewModel<NestedViewModel>();
if (viewModel.Others.Single().Name == "Bobby")
    viewModel.Name = "Definitely not Timmy";
var dto2 = viewModel.ToDto<NestedTransferDataObject>();