private void UnregisterEventHandlers ()
{
// dataTable.ColumnChanging -= new DataColumnChangeEventHandler(OnColumnChanging);
dataTable.ColumnChanged -= new DataColumnChangeEventHandler(OnColumnChanged);
dataTable.RowChanged -= new DataRowChangeEventHandler(OnRowChanged);
// dataTable.RowDeleting -= new DataRowChangeEventHandler(OnRowDeleting);
dataTable.RowDeleted -= new DataRowChangeEventHandler(OnRowDeleted);
dataTable.Columns.CollectionChanged -= new CollectionChangeEventHandler(ColumnCollectionChanged);
dataTable.Columns.CollectionMetaDataChanged -= new CollectionChangeEventHandler(ColumnCollectionChanged);
dataTable.Constraints.CollectionChanged -= new CollectionChangeEventHandler(OnConstraintCollectionChanged);
dataTable.ChildRelations.CollectionChanged -= new CollectionChangeEventHandler(OnRelationCollectionChanged);
dataTable.ParentRelations.CollectionChanged -= new CollectionChangeEventHandler(OnRelationCollectionChanged);
dataTable.Rows.ListChanged -= new ListChangedEventHandler (OnRowCollectionChanged);
}