包含在EF 6.2中，不获取子实体（非ef net核心）

Question

我定义了以下类

文档类型

   public class DocumentType
    {
        [DataMember]
        [Key]
        [ScaffoldColumn(false)]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int Id { get; set; }

        [Required]
        [MaxLength(100, ErrorMessage = "The field Name must be maximum length of '100'.")]
        public string Name { get; set; }

        [MaxLength(200, ErrorMessage = "The field Description must be maximum length of '200'.")]
        public string Description { get; set; }
        [Required]
        [MaxLength(30, ErrorMessage = "The field Category must be maximum length of '30'.")]
        [Display(Name = "Category")]
        public string CategoryName { get; set; }

        [ScaffoldColumn(false)]
        public bool IsDeleted { get; set; }

        public virtual List<DocumentApplicability> DocumentApplicabilities { get; set; }
        public virtual List<DocumentField> DocumentFields { get; set; }


    }

文档类型字段

 public class DocumentField 
    {

        public int DocumentTypeID { get; set; }
        [ForeignKey("DocumentTypeID")]
        public DocumentType DocumentType { get; set; }

        [DataMember]
        [Key]
        [ScaffoldColumn(false)]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int Id { get; set; }

        [Required]
        [MaxLength(30, ErrorMessage = "The field Name must be maximum length of '30'.")]
        public string Name { get; set; }

        [MaxLength(150, ErrorMessage = "The field Description must be maximum length of '150'.")]
        public string Description { get; set; }

    }

我从未看到填充过的文档字段。 Sql server告诉我db中有记录，但是当我在调用下面的函数后尝试使用此信息时，对于已记录的字段，我总是会得到null。

 public static void GetDocumentTypes()
    {
     ef.DataContext d = new ef.DataContext();
     var qry = (from adoctype in d.DocumentType select adoctype);
     qry.Include("DocumentFields");
     var q = qry.ToList();
     Debug.WriteLine("done");
    }

有人可以帮忙吗