实体框架 - 包含多个级别属性

Question

我试图使用实体框架从数据库中获取一个表.

该表引用了另一个表,该表再次引用了其他表.我知道如何包含其他表格.根据这个答案,这个包含多个级别的MSDN页面是这样的:

entity.TableLevel1.Include(tLvl1=>tLvl1.TableLevel2.Select(tLvl2=>tLvl2.TableLevel3));

但我的问题是,如何在3级包含另一张表？

这似乎不起作用:

entity.TableLevel1
          .Include(tLvl1=>tLvl1.TableLevel2
               .Select(tLvl2=>tLvl2.TableLevel3)
               .Select(tLvl2 => tLvl2.AnotherTableLevel3);

Answer 1

添加另一个Include电话:

entity.TableLevel1.Include(tLvl1=>tLvl1.TableLevel2.Select(tLvl2=>tLvl2.TableLevel3))
                  .Include(tLvl1=>tLvl1.TableLevel2.Select(tLvl2=>tLvl2.AnotherTableLevel3));

如果要加载相同级别的相关实体,则应Include为每个实体调用 扩展方法.

Answer 2

你可以打多个Include()电话:

entity.TableLevel1.Include(t1 => t1.TableLevel2);
entity.TableLevel1.Include(t1 => t1.TableLevel2.Select(t2 => t2.TableLevel3));
entity.TableLevel1.Include(t1 => t1.TableLevel2.Select(t2 => t2.AnotherTableLevel3));

要么

entity.TableLevel1.Include("TableLevel2");
entity.TableLevel1.Include("TableLevel2.TableLevel3");
entity.TableLevel1.Include("TableLevel2.AnotherTableLevel3");

但是您可以将导航属性标记为virtual延迟加载,因此您无需Include()拨打电话:

class TableLevel1
{
    public virtual TableLevel2 TableLevel2 { get; set; }
}

class TableLevel2
{
    public virtual TableLevel3 TableLevel3 { get; set; }

    public virtual TableLevel3 AnotherTableLevel3 { get; set; }
}