Detailed explanation of the differences between .Remove() and .DeleteObject() methods in Entity Framework

In Entity Framework, there are two options for removing items from the database: .Remove() and .DeleteObject(). Although both methods target database operations, subtle differences determine their applicable scenarios.

ObjectContext.DeleteObject()

ObjectContext.DeleteObject() Marks the entity for deletion in the context. This operation sets the entity's EntityState to Deleted. After calling SaveChanges, EF dispatches a SQL DELETE statement to the database. However, if any reference constraints are violated, an exception will be thrown, preventing the deletion.

EntityCollection.Remove()

EntityCollection.Remove() Marks the relationship between the parent entity and the child entity as Deleted. This operation itself does not directly delete the child entity from the database. Depending on the underlying relationship, different situations will occur:

• Optional relationship: foreign key is set to NULL, SaveChanges will update the database accordingly.
• Required non-identifying relationship: You must attach the child to a new parent or delete it explicitly using DeleteObject(). Otherwise, reference constraint conflicts will occur.
• identifies the relationship: The child entity is also marked for deletion, triggering the SQL DELETE statement during SaveChanges.

Return value and usage

.Remove() returns a Boolean value indicating success, while .DeleteObject() is of void type. Essentially, .Remove() modifies relationships, while .DeleteObject() operates directly on entities.

So if you plan to delete entities directly from the database, use .DeleteObject(). However, if you wish to modify relationships between entities without having to remove child entities, .Remove() is preferred.

Please note that the MSDN notes section on the .Remove() method is somewhat vague about referential integrity constraints. While all three relationship types have constraints, child entities are only actually deleted if the relationship is identified.