具有EF6子集合的父/子始终为null

Question

When ever I pull a MyList object via EF, the parent is associated correctly but the Children collection is always null. Not sure what I'm doing wrong, pretty much every article shows to do it this way.

Database

CREATE TABLE [dbo].[MyList] (
    [MyListId]     BIGINT           IDENTITY (1, 1) NOT NULL,
    [ParentMyListId] BIGINT NULL, 
    CONSTRAINT [PK_MyList] PRIMARY KEY CLUSTERED ([MyListId] ASC) WITH (FILLFACTOR = 90),
    CONSTRAINT [FK_MyList_MyList_MyListId] FOREIGN KEY (ParentMyListId) REFERENCES MyList(MyListId)
);

Model

public class MyList
{
    [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public long MyListId { get; set; }
    public long? ParentMyListId { get; set; }

    [ForeignKey("ParentMyListId")]
    public virtual List MyListParent { get; set; }

    public virtual ICollection<MyList> MyListChildren { get; set; }
}

DBContext

public class MyContext : DbContext
{
    public MyContext() : base(Properties.Settings.Default.DbContext)
    {
        Configuration.LazyLoadingEnabled = false;
    }

    public DbSet<MyList> MyLists { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<MyList>()
        .ToTable("MyList", "dbo")
        .HasOptional(x => x.MyListParent)
        .WithMany(x => x.MyListChildren)
        .HasForeignKey(x => x.ParentMyListId)
        .WillCascadeOnDelete(false);
    }

    base.OnModelCreating(modelBuilder);
}

Answer 1

I tried with same structure in EF 6.1.3 version and it worked like charm. I added image of output and data present in db. The only thing that might stopped working if you disable loading in configuration. I hope it work for you please try my sample code.

  // Your entity class I added name property to show you the results 
   public class MyList
    {
        [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public long MyListId { get; set; }
        public long? ParentMyListId { get; set; }

        public string Name { get; set; }

        [ForeignKey("ParentMyListId")]
        public virtual MyList MyListParent { get; set; }

        public virtual ICollection<MyList> MyListChildren { get; set; }
    }       

     // DBContext please note no configuration properties set just default constructor 
     // you need t check here if you have set soemthing here 
       public class TestContext : DbContext
        {
            public TestContext()
                : base("name=TestConnection")
            {
            }               

            protected override void OnModelCreating(DbModelBuilder modelBuilder)
            {
                modelBuilder.Entity<MyList>()
                .ToTable("MyList", "dbo")
                .HasOptional(x => x.MyListParent)
                .WithMany(x => x.MyListChildren)
                .HasForeignKey(x => x.ParentMyListId)
                .WillCascadeOnDelete(false);

            }

            public virtual DbSet<MyList> Lists { get; set; }
        }

The console app to show result:

    static void Main(string[] args)
    {
        using (var ctx = new TestContext())
        {

            // for testing to see al working 
            //this is important to read the entity first .
            var parent = ctx.Lists.ToList();

            foreach (var p in parent)
            {
                foreach (var child in p.MyListChildren)
                {
                    Console.WriteLine(string.Format(@"Parent Name {0}  has child with name {1}", p.Name, child.Name));
                }
            }

        }

        Console.ReadLine();
    }

Output of app and data in database ...