实体框架多个级联路径错误

Question

What I've done so far to achieve what I want using Entity Framework is something like this:

// User.cs
public class User {
  public Guid ID { get; set; } // column: user_id
  public virtual ICollection<Event> Events { get; set; }
}
// Event.cs
public class Event {
  public Guid ID { get; set; } // column: event_id
  public virtual Guid UserID { get; set; } // column: event_userid
  public virtual ICollection<User> Guests { get; set; }
}
// MyAppContext.cs
...
protected override void OnModelCreating(DbModelBuilder mb) {
  mb.Entity<User>()
    .HasKey(u => u.ID)
    .HasMany(u => u.Events)
    .WithOptional()
    .HasForeignKey(e => e.UserID);

  mb.Entity<Event>()
    .HasKey(e => e.ID)
    .HasMany(e => e.Guests)
    .WithMany();
}
...

I was expecting the database structure to be as follows:

TABLE: user
user_id uniqueidentifier not null primary key

TABLE: event
event_id uniqueidentifier not null primary key
event_userid uniqueidentifier not null foreign key references user(user_id)

TABLE: event_guests
event_id uniqueidentifier not null
user_id uniqueidentifier not null

I have a feeling that the fluent API I'm using above is not going to give the expected database structure and also, I get the following exception that I've no clue how to fix:

Introducing FOREIGN KEY constraint 'FK_xxx' on table 'event_guests'
may cause cycles or multiple cascade paths. Specify ON DELETE NO
ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.
Could not create constraint. See previous errors.

I'm new to entity framework, any help would be much appreciated.

Answer 1

Try replacing your configurations with a single many to many configuration.

modelBuilder.Entity<User>()
            .HasMany(a => a.Events)
            .WithMany(b=> b.Guests)
            .Map(x =>
            {
                x.MapLeftKey("UserId");
                x.MapRightKey("EventId");
                x.ToTable("EventGuests");
            });