Code First: Independent associations vs. Foreign key associations?

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Independent association doesn’t work well with AddOrUpdate that is usually used in Seed method. When the reference is an existing item, it will be re-inserted.

// Existing customer.
var customer = new Customer { Id = 1, Name = "edit name" };
db.Set<Customer>().AddOrUpdate(customer);

// New order.
var order = new Order { Id = 1, Customer = customer };
db.Set<Order>().AddOrUpdate(order);

The result is existing customer will be re-inserted and new (re-inserted) customer will be associated with new order.

Unless we use the foreign key association and assign the id.

 // Existing customer.
var customer = new Customer { Id = 1, Name = "edit name" };
db.Set<Customer>().AddOrUpdate(customer);

// New order.
var order = new Order { Id = 1, CustomerId = customer.Id };
db.Set<Order>().AddOrUpdate(order);

We have the expected behavior, existing customer will be associated with new order.

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