public class ViewModelLocator
{
    public ViewModelLocator()
    {
        SimpleIoc.Default.Register<MainViewModel>();
        SimpleIoc.Default.Register<EditorViewModel>();
    }

    public MainViewModel Main => ServiceLocator.Current.GetInstance<MainViewModel>();

    public EditorViewModel Editor => ServiceLocator.Current.GetInstance<EditorViewModel>();
}

public MainViewModel Main => new MainViewModel();

    public EditorViewModel Editor => new EditorViewModel();