public bool Add(TableColumn col)
{
if (_index == null) _index = new Dictionary<string, int>();
if (_index.ContainsKey(col.Name)) return false;
TableColumn c = new TableColumn(col);
_cols.Add(c);
_index.Add(c.Name, _cols.Count - 1);
return true;
}
public TableColumn(TableColumn s)
{
_name = s._name;
_dataType = s._dataType;
_indexed = s.Indexed;
}