/// <summary>
        /// Called when the columns need to be populated.
        /// </summary>
        /// <param name="listModel"></param>
        /// <param name="e"></param>
        private void Chain_FetchColumns(TListModel listModel, ListContentEventArgs e)
        {
            _BaseFetchColumns(listModel, e);

            var identifier = GetListIdentifierAction(listModel);
            var inSubset   = ModelSubsetList.Contains(identifier);

            e.Checked = inSubset;
        }
        /// <summary>
        /// Called when the checked state is changed in the list.
        /// </summary>
        /// <param name="listModel"></param>
        /// <param name="isChecked"></param>
        private void Base_CheckedChangedHandler(TListModel listModel, bool isChecked)
        {
            var identifier = GetListIdentifierAction(listModel);

            if (isChecked && !ModelSubsetList.Contains(identifier))
            {
                ModelSubsetList.Add(identifier);
            }
            if (!isChecked && ModelSubsetList.Contains(identifier))
            {
                ModelSubsetList.Remove(identifier);
            }
        }