public void Selected(ContractMembershipDTO model)
        {
            var _model = source.Where(o => o.Id == model.Id).FirstOrDefault();

            if (_model is null)
            {
                return;
            }
            _model.Selected = !_model.Selected;
            _model.render();
            int index = source.IndexOf(_model);

            if (index < 0)
            {
                return;
            }

            source[index] = _model;
        }
        public void OnItemTapped(object sender, ItemTappedEventArgs e)
        {
            ContractMembershipDTO item = e.Item as ContractMembershipDTO;

            modelContext.Selected(item);
        }
        public void OnItemSelected(object sender, SelectedItemChangedEventArgs e)
        {
            ContractMembershipDTO item = e.SelectedItem as ContractMembershipDTO;

            modelContext.Selected(item);
        }