Aggregation implies a relationship where the child can exist independently of the parent. Aggregations are weak relations because B and A are independent and it is also known as "Has a" relationship.
Composition implies a relationship where the child cannot exist independent of the parent. Compositions are strong because B cannot exist without A, and is also known as the "Owns a" relationship.
You can configure the Aggregations and Compositions using the [Aggregation] and [Composition] attributes on the corresponding properties.
public class Author
{
public int AuthorId { get; set; }
public string Name { get; set; }
[Composition]
public virtual ICollection<Book> Books { get; set; }
}
Associations must be configured as aggregations or compositions, so Detached can choose how to load and map them. You can also configure it using fluent API by using MappingOptions when calling UseDetached to configure it as shown below.
public class BookStore : DbContext
{
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder
.UseSqlServer(@"Data Source=(localdb)\ProjectsV13;Initial Catalog=BookStoreDb;")
.UseDetached(options => {
options.Configure<Author>().Member(a => a.Books).Composition();
});
}
public DbSet<Author> Authors { get; set; }
public DbSet<Book> Books { get; set; }
}
Unmodified.