CODEWITHSUNDEEP
entity-framework-6.1
MrLane
MrLane

Reputation: 1728

Entity Framework Cascade Deleting, even though no CASCADE set up in database

I have a foreign key relationship between two tables UserProducts and Users in my database, with UserProducts having a UserID referencing the UserID in the Users table.

ALTER TABLE [dbo].[UserProducts]  WITH CHECK ADD  CONSTRAINT [FK_UserProducts_Users] FOREIGN KEY ([UserID])
REFERENCES [dbo].[Users] ([UserID])
GO

ALTER TABLE [dbo].[UserProducts] CHECK CONSTRAINT [FK_UserProducts_Users]
GO

The UserID column in the UserProducts table is part of a composite primary key with another column ProductID. There are also two additional DateTime columns, so Entity Framework does not treat UserProducts as a link table.

There is NO cascade delete on that foreign key above, nor did I set up anything to handle OnDelete on the Entity Framework foreign key association. Yet, when I delete a User entity from code, Entity Framework is taking the liberty of deleting the UserProducts associated with it by UserID. It is also generating a lot of SQL to do it: there is a separate DELETE per related record in the UserProducts table.

The code to perform the entity deletion is as follows:

using (var context = new LicensingRegistrationContext(_csb))
{
    context.Database.Log = a => _logger.Trace(a);

    var dbUser = GetUserDbSetWithIncludes(context)
        .Where(a => a.UserID == user.Id).Single();

    context.DbUsers.Remove(dbUser);

    //TODO(MRL): Um...how are the dbUserProducts being removed???

    context.SaveChanges();
}

How is this happening? In EF 4 I am pretty sure EF never took this liberty of doing this: you HAD to load and then delete all related entities manually in code.

Thanks

Upvotes: 0

Views: 608

Answers (2)

MrLane
MrLane

Reputation: 1728

I found this on MSDN and I believe this is what is happening:

When a primary key of the principal entity is also part of the primary key of the dependent entity, the relationship is an identifying relationship. In an identifying relationship the dependent entity cannot exist without the principal entity. This constraint causes the following behaviors in an identifying relationship: Deleting the principal object also deletes the dependent object. This is the same behavior as specifying OnDelete Action="Cascade" in the model for the relationship. Removing the relationship deletes the dependent object. Calling the Remove method on the EntityCollection marks both the relationship and the dependent object for deletion.

This is what is happening in my model where the UserComponent table has a composite primary key: UserID, ComponentID and the UserID column is a foreign key to the UserID in the User table.

Upvotes: 0

user2635176
user2635176

Reputation:

Entity framework by default has a 

OneToManyCascadeDelete

convention. Here is the link http://msdn.microsoft.com/en-us/library/system.data.entity.modelconfiguration.conventions.onetomanycascadedeleteconvention(v=vs.113).aspx

So entity framework cascade deletes the one to many relationship by default.

You can disable this by disabling the convention or explicitly disabled it for this relationship via the fluent API.

Upvotes: 1

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