Pattern D: 親子一体 CRUD（マスター明細）

To save a parent entity and multiple child items in one transaction with EF Core, you model the parent as an aggregate root that encapsulates a collection of child entities, ensuring atomic CRUD operations and consistency across the aggregate.

The best way to handle master-detail CRUD in domain-driven design is to model the parent as an aggregate root, encapsulate the child entities, and enforce invariants within the domain while persisting the entire aggregate atomically through a repository.

You need an aggregate root for parent-child data persistence when a single screen operation must create or update a header with a variable number of line items, requiring strict consistency across the entire aggregate during the transaction.

Yes, you can update a variable number of child rows atomically with a parent header in EF Core by using command handlers to manage create, update, and delete operations for the aggregate root and persisting them together in one transaction.

Command handler based persistence for master-detail aggregates works by receiving create, update, or delete commands, applying them to the aggregate root and its child entities, and then using a repository to commit the entire aggregate in a single EF Core transaction.