在使用EF Fluent API映射我的实体关系时，我是否需要同时映射涉及的两个实体？

Question

I'm creating the entity relationships using Code First with EF Fluent API following the instructions from this tutorial to create the 1:n and m:n relationships in my model.

What I'm wondering and haven't found a response searching, is that if it's required to define the relationship on both ends of it.

By that I mean, if I have an entity called User and Organization, there are two relationships involving these two entities as I described below:

• An User can many Organizations, while an Organization must be owned by one User.
• An User may be present in many Organizations, while an Organization may have many Users in it.

With this in mind, I defined the relationships using Fluent API as follows:

        modelBuilder.Entity<Organization>().HasRequired(o => o.Owner).WithMany(u => u.OrganizationsOwned).WillCascadeOnDelete(false);

        modelBuilder.Entity<User>().HasMany<Organization>(u => u.Organizations).WithMany(o => o.Users).Map(uo =>
        {
            uo.MapLeftKey("UserId");
            uo.MapRightKey("OrganizationId");
            uo.ToTable("OrganizationsUsers");
        });

But are these definitions enough? Or do I have to define the relationships on the other end of the entities too? What I mean, do I need to add the following code?

        modelBuilder.Entity<User>().HasMany(u => u.OrganizationsOwned).WithRequired(o => o.Owner).WillCascadeOnDelete(false);

        modelBuilder.Entity<Organization>().HasMany<User>(o => o.Users).WithMany(u => u.Organizations).Map(ou =>
        {
            ou.MapLeftKey("UserId");
            ou.MapRightKey("OrganizationId");
            ou.ToTable("OrganizationsUsers");
        });

Answer 1

Yes, these definitions are enough. You are defining both sides of the relationship with the single statement:

.Entity<Organization>().HasRequired(o => o.Owner).WithMany(u => u.OrganizationsOwned)

The .HasRequired defines the 1 side, and the .WithMany defines the Many side. There is only one relationship, but two sides. You can define the relationship from either side, but you do not have to define it from both.