ForeignKey-多对多（EntityFramework）中的定义？

Question

Because I don't like the naming convention the entityFramework (Code first) uses I usually use a foreignKey property to assign my own property:

public class User {
   public virtual Customer Customer { get; set; }
   [ForeignKey("Customer")]
   public Guid CustomerId { get; set; }
}

Works just fine, a column "CustomerId" is created inside the "User"-Table.

But how do I achieve the same when I need a many-to-many relationship?

public class User {
       public virtual ICollection<Role> Roles { get; set; }
    }

public class Role {
   public virtual ICollection<User> Users { get;set; }
}

This results in a Table "UserRole" which contains "User_id" and "Role_Id".

Still, I prefer "UserId" and "RoleId". I could just create a UserRole-Class myself containing the references to User and Role but there should be a more elegant way. Is there any?

Answer 1

You could configure that many-to-many relationship on your context using Fluent Api as I show below:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{

   modelBuilder.Entity<User>()
               .HasMany<Role>(u => u.Roles)
               .WithMany(c => c.Users)
               .Map(cs =>
                        {
                            cs.MapLeftKey("UserId");
                            cs.MapRightKey("RoleId");
                            cs.ToTable("UserRoles");
                        });

}

This way you could name the junction table and the FK columns with the names that you want.

Another way is create an entity that represent the junction table and stablish two one-to-many relationships with User and Role , but if you don't need to add extra columns to the junction table, It's recommended use the first variant, but you can find some advantages in map this table explicitly.