AddObject vs. Attach in Entity Framework 4: When to Use Which Method?

Entity Framework 4: AddObject vs. Attach

Entity Framework 4 offers two key methods for entity management: AddObject and Attach. The choice depends on whether the entity already exists in the database.

AddObject:

Use AddObject to insert a completely new entity into the database. The entity receives a temporary EntityKey and its state is set to Added. Calling SaveChanges then persists this new entity to the database.

Attach:

Use Attach for entities that already reside in the database. This method assumes the entity's existence, sets its state to Unchanged, and enables modifications. Invoking SaveChanges utilizes the EntityKey to update or delete the corresponding database record.

Beyond adding new entities, Attach proves invaluable for managing relationships between entities already within the ObjectContext but lacking automatic links. For example, if a Person entity has an Addresses property, Attach facilitates connecting detached Address entities to the Person object.

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