EntityFramework导航属性未按预期工作

Question

我在实体框架中设置了以下3个（简化）类

public class Service
{
    [Key]
    public int ServiceId { get; set; }
    public int WorkformId { get; set; }

    [ForeignKey("WorkformId")]
    public virtual Workform Workform { get; set; }
}


public class Workform
{
    [Key]
    public int WorkformId { get; set; }

    [ForeignKey("WorkformId")]
    public virtual ICollection<FieldMap> FieldMaps { get; set; }
 }


public class FieldMap
{
    [Key]
    public int FieldMapId{ get; set; }
    public int WorkformId{ get; set; }
 }

如果我尝试做这样的事情

var service = db.Services.Include("Workform.FieldMaps")
                .FirstOrDefault(p => p.ServiceId == serviceId);

service.Workform.FieldMaps正在拉动整个集合，而不仅仅是具有匹配关系id的记录。

我在这里错过了一些吗？