WCF+EF的一个问题

实体：

[Serializable]    [DataContract]    public class Employee    {        [DataMember]        [Key]        [Required]        public int ID { get; set; }        [DataMember]        public string Name { get; set; }        [DataMember]        public string PosName { get; set; }        [DataMember]        public int? Gender { get; set; }            }

接口：

[OperationContract]        IQueryable<Employee> GetEmps(int organzationId);

实现：

public IQueryable<Employee> GetEmps(int organzationId)        {            return _objContext.ExecuteStoreQuery<Employee>("select u.ID,e.Name,P.Name as PosName,e.Gender from sys_user u inner join hr_employee e on u.ID=e.[User] inner join hr_Position p on e.Position=p.ID where u.Forbidden=0 and e.Organization=@orgid", new SqlParameter("@orgid", organzationId)).AsQueryable();        }

运行，没有问题，但是在实体里增加一个byte[]类型的属性，如下：

[Serializable]    [DataContract]    public class Employee    {        [DataMember]        [Key]        [Required]        public int ID { get; set; }        [DataMember]        public string Name { get; set; }        [DataMember]        public string PosName { get; set; }        [DataMember]        public int? Gender { get; set; }        [DataMember]        public byte[] Photo { get; set; }    }

运行，报错：服务积极拒绝。但是调试服务端，并不出错。经尝试，将接口改成如下：

[OperationContract]        IList<Employee> GetEmps(int organzationId);

实现改成如下：

public IList<Employee> GetEmps(int organzationId)        {            return _objContext.ExecuteStoreQuery<Employee>("select u.ID,e.Name,P.Name as PosName,e.Gender,e.Photo from sys_user u inner join hr_employee e on u.ID=e.[User] inner join hr_Position p on e.Position=p.ID where u.Forbidden=0 and e.Organization=@orgid", new SqlParameter("@orgid", organzationId)).ToList();        }

运行OK。

分析：应该是执行AsQuery操作是延迟加载数据，而执行ToList操作则立即加载数据。但是为什么在无byte[]类型的属性时就能正常运行，我还没弄明白。