How to access a field/property of a BlockList: Activity view window, given an Activity reference passed (Xamarin.Android)?

Question

Android

It is necessary for Xamarin.Android.
How to refer to lblListHeader, lvExp in the method public override View GetGroupView ???

public class BlockList : Activity
{            
        ExpandableListAdapter listAdapter;
        ExpandableListView expListView;

        public ExpandableListView lvExp;
        public TextView lblListHeader;
        public TextView lblListItem;

        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);

            // Create your application here
            SetContentView(Resource.Layout.BlockList); // загружаем наш Активити (страницу xml) из папки Resources.Layout
...
            listAdapter = new ExpandableListAdapter(this, listDataHeader, listDataChild);
            expListView.SetAdapter(listAdapter);
}

public class ExpandableListAdapter : BaseExpandableListAdapter
    {
        private Activity _context;
        private List<string> _listDataHeader; // header titles
                                              // child data in format of header title, child title
        private Dictionary<string, List<string>> _listDataChild;

        public ExpandableListAdapter(Activity context, List<string> listDataHeader, Dictionary<String, List<string>> listChildData)
        {
            _context = context;
            _listDataHeader = listDataHeader;
            _listDataChild = listChildData;
        }
        public override View GetGroupView(int groupPosition, bool isExpanded, View convertView, ViewGroup parent)
        {
...     <i><b>Как здесь обратиться к lblListHeader, lvExp ???</b></i>
         }

Or do you need to transfer the BlockList itself?

2 question: how to access BlockList from MainPage ?

public class MainActivity : AppCompatActivity
    {
        public static MainActivity MainActivityInstance { get; private set; }
        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            Xamarin.Essentials.Platform.Init(this, savedInstanceState);
            MainActivityInstance = this;

            // Create your application here
            Intent intent = new Intent(this, typeof(BlockList)); // загружаем наш класс для Активити typeof(RetryPage)
            StartActivity(intent);

All this is needed without XAMl. It's so clear with him