EF Code First - WithMany()

Question

I recently came by the class ManyNavigationPropertyConfiguration , and within that class there I found a method named WithMany()

Answer 1

An example might be this model:

public class User
{
    public int UserId { get; set; }
    public string Name { get; set; }
    public ICollection Roles { get; set; }
}

public class Role
{
    public int RoleId { get; set; }
    public string Description { get; set; }
}

If you are never interested to retrieve all users which are in a specific role, adding a navigation property ...

public ICollection Users { get; set; }

... to the Role class would be unnecessary overhead.

But you still must EF tell that a many-to-many relationship between User and Role exists ...

modelBuilder.Entity()
            .HasMany(u => u.Roles)
            .WithMany();

... because the default convention mappings would create a wrong relationship, namely a one-to-many relationship, corresponding to this mapping:

modelBuilder.Entity()
            .HasMany(u => u.Roles)
            .WithOptional();