Помогите с С#
 

Пропустил в колледже пару тем и вообще сейчас не понимаю заданную задачу .
Помогите пожалуйста.:tehnari_ru_837:

что делает этот блок?
#region Заполнение PreviewFactTGV
PreviewFactTGV.Nodes.Clear();
List<Pos_group> listPos_group2 = connector.getAllDataFromDB("Pos_group AS pg WHERE pg.pt_pt_id=2 AND pg.cs_cs_id = " + (mainDGV.Rows[RowForDetail].Tag as Contract_spec).cs_id).ConvertAll(new Converter<object, Pos_group>(ConverterPos_group));
for (int j = 0; j < listPos_group2.Count; j++)
{
TreeGridNode node = PreviewFactTGV.Nodes.Add(listPos_group2[j].name);
node.Tag = listPos_group2[j];
NodeCellsToTextBoxCells(node);
List<Positions> listPositionsDocs = connector.getAllDataFromDB("Positions AS pos WHERE pos.del IS NULL AND pos.post_post_id=2 AND pos.pos_pos_id IS NULL AND pos.pg_pg_id = " + listPos_group2[j].pg_id + "AND pos.cs_cs_id = " + ((Contract_spec)mainDGV.Rows[RowForDetail].Tag).cs_id + " ORDER BY pos.order_number asc").ConvertAll(new Converter<object, Positions>(ConverterPositions));
for (int i = 0; i < listPositionsDocs.Count; i++)
{
TreeGridNode nodeChild = node.Nodes.Add(listPositionsDocs[i].article, listPositionsDocs[i].name, listPositionsDocs[i].um_um_id.short_name, listPositionsDocs[i].count,
listPositionsDocs[i].val_val_id.name, listPositionsDocs[i].price, listPositionsDocs[i].summa, listPositionsDocs[i].stat_stat_id.name, listPositionsDocs[i].delivery,
listPositionsDocs[i].cancel, listPositionsDocs[i].official);
nodeChild.Tag = listPositionsDocs[i];
recursionAddingNodes(nodeChild, listPositionsDocs[i].pos_id, listPositionsDocs[i].post_post_id, listPositionsDocs[i].pg_pg_id);
}
}

#endregion
}
canTrackMainTGVChanges = true;
}

private void NodeCellsToTextBoxCells(TreeGridNode treeGridNode)
{
for (int i = 1; i < treeGridNode.Cells.Count; i++)//Заполнение пустыми ячейками строки группы
{
treeGridNode.Cells[i] = new DataGridViewTextBoxCell();
treeGridNode.Cells[i].Value = "";
treeGridNode.Cells[i].ReadOnly = true;
}
}
//Рекурсивно добавляем потомков в дерево
private void recursionAddingNodes(TreeGridNode node, int id, Pos_type pos_type, Pos_group pos_group)
{
List<Positions> listPositionsChildren = connector.getAllDataFromDB("Positions AS pos WHERE pos.del IS NULL AND pos.post_post_id=" + pos_type.pos_type_id + " AND pos.pg_pg_id = " + pos_group.pg_id + " AND pos.pos_pos_id = " + id + " ORDER BY pos.order_number asc").ConvertAll(new Converter<object, Positions>(ConverterPositions));
for (int j = 0; j < listPositionsChildren.Count; j++)
{
TreeGridNode nodeChild = node.Nodes.Add(listPositionsChildren[j].article, listPositionsChildren[j].name, listPositionsChildren[j].um_um_id.short_name, listPositionsChildren[j].count,
listPositionsChildren[j].val_val_id.name, listPositionsChildren[j].price, listPositionsChildren[j].summa, listPositionsChildren[j].stat_stat_id.name, listPositionsChildren[j].delivery,
listPositionsChildren[j].cancel, listPositionsChildren[j].official);
nodeChild.Tag = listPositionsChildren[j];

Positions newPos = new Positions();
newPos.name = ((Positions)nodeChild.Tag).name;
newPos.article = ((Positions)nodeChild.Tag).article;
newPos.cancel = ((Positions)nodeChild.Tag).cancel;
newPos.count = ((Positions)nodeChild.Tag).count;
newPos.delivery = ((Positions)nodeChild.Tag).delivery;
newPos.official = ((Positions)nodeChild.Tag).official;
newPos.delivery = ((Positions)nodeChild.Tag).delivery;
newPos.price = ((Positions)nodeChild.Tag).price;
newPos.summa = ((Positions)nodeChild.Tag).summa;
newPos.stat_stat_id = ((Positions)nodeChild.Tag).stat_stat_id;
newPos.prop_prop_id = ((Positions)nodeChild.Tag).prop_prop_id;
newPos.um_um_id = ((Positions)nodeChild.Tag).um_um_id;
newPos.val_val_id = ((Positions)nodeChild.Tag).val_val_id;

newPos.pg_pg_id = ((Positions)nodeChild.Parent.Tag).pg_pg_id;
newPos.post_post_id = ((Positions)nodeChild.Parent.Tag).post_post_id;
newPos.pos_pos_id = ((Positions)nodeChild.Parent.Tag);
newPos.cs_cs_id = ((Positions)nodeChild.Parent.Tag).cs_cs_id;
recursionAddingNodes(nodeChild, listPositionsChildren[j].pos_id, listPositionsChildren[j].post_post_id, listPositionsChildren[j].pg_pg_id);
}
}
#endregion

private void mainDGV_CellMouseDoubleClick(object sender, DataGridViewCellMouseEventArgs e)
{
var newTab = new DogovornieSpecifikaciiForm(mainDGV.Rows[e.RowIndex].Tag as Contract_spec);
(Parent as ExtendedTabControl).TabPages.Add(newTab);
(Parent as ExtendedTabControl).SelectedTab = newTab;
}
}
}