public IEnumerable <T> GetColumns() => _columns; // return just its own columns
// return all columns of a column subset (inherited + its own)
// just for test purposes
public IEnumerable <T> GetColumnsIncludeInherited()
{
var allColumns = _parent?.GetColumns() as List <T> ?? new List <T>();
foreach (var column in _columns)
{
allColumns.Add(column);
}
return(allColumns);
}
public void SetParentSubset(IColumnSubsetInfo <T> parent)
{
if (GetParentSubset() != null)
{
throw new Exception($"Subset {this} already has a parent subset.");
}
_parent = parent;
// when assigning a parent, remove all columns inherited from this parent, so a 'derived' object contains only its own columns
_columns = _columns.Except(parent.GetColumns()).ToList();
}
