private void FindDroppedForeignKeys(
Tuple <IEntityType, IEntityType> tablePair,
IEnumerable <Tuple <IForeignKey, IForeignKey> > foreignKeyPairs)
{
_operations.AddRange(
tablePair.Item1.ForeignKeys
.Except(foreignKeyPairs.Select(pair => pair.Item1))
.Select(fk => OperationFactory.DropForeignKeyOperation(fk)));
}