Would it be possible to modify or post an update to this article with the LinqDataSource as the provider?
Or just point us in the right direction for the DeleteCommand syntax.
If you have access to your SQL database, you can set the ON DELETE CASCADE constraint for the relation linking your parent and detail tables. This will automatically have your database delete the related records.
If this is not a suitable approach for you, we best advise you to manually delete your related items again using LINQ from the data context object you have created for LinqDataSource.
You can find attached a small web site where I demonstrate how you can cascade delete your nested items manually from the same DataContext object the LinqDataSource is using.