Question

我有一个抽象的Entity类，我的所有实体都是从这个类派生出来的。此基类具有CreatedBy和ModifiedBy属性，均为AppUser类型。由于AppUser也继承自Entity，我想知道这种循环是否令EF感到困惑。这是我的班级定义：

public abstract class Entity
{
    [Index(IsUnique = true)]
    public int Id { get; set; }
    [Required]
    public DateTime CreatedOn { get; set; }
    [Required]
    public DateTime ModifiedOn { get; set; }
    public AppUser CreatedBy { get; set; }
    public AppUser ModifiedBy { get; set; }
}

当我致电context.Users.ToArray()时，它会返回：

IsActive Identifier FirstName LastName MiddleName Id 
False    ee224559   bob       jones               1  
False    ee224559   bob       jones               1  
False    ee224559   bob       jones               1  
False    ee224559   bob       jones               1  
False    dheyue3    mary      smith    sue        21 
False    dheyue3    sarah     jones               22

这是它生成的SQL：

SELECT 
"Extent1"."FIRSTNAME" AS "FIRSTNAME",
"Extent2"."FIRSTNAME" AS "CREATEDBY",
"Extent3"."FIRSTNAME" AS "MODIFIEDBY"
FROM   "MYSCHEMA"."APPUSER" "Extent1"
LEFT OUTER JOIN "MYSCHEMA"."APPUSER" "Extent2" ON 
("Extent2"."CREATEDBY_ID" IS NOT NULL) AND ("Extent1"."ID" = "Extent2"."CREATEDBY_ID")
LEFT OUTER JOIN "MYSCHEMA"."APPUSER" "Extent3" ON 
("Extent3"."MODIFIEDBY_ID" IS NOT NULL) AND ("Extent1"."ID" = "Extent3"."MODIFIEDBY_ID");

这就是我想要它生成的内容：

SELECT 
"Extent1"."FIRSTNAME" AS "FIRSTNAME",
"Extent2"."FIRSTNAME" AS "CREATEDBY",
"Extent3"."FIRSTNAME" AS "MODIFIEDBY"
FROM   "MYSCHEMA"."APPUSER" "Extent1"
LEFT OUTER JOIN "MYSCHEMA"."APPUSER" "Extent2" ON 
("Extent1"."CREATEDBY_ID" IS NOT NULL) AND ("Extent2"."ID" = "Extent1"."CREATEDBY_ID")
LEFT OUTER JOIN "MYSCHEMA"."APPUSER" "Extent3" ON 
("Extent1"."MODIFIEDBY_ID" IS NOT NULL) AND ("Extent3"."ID" = "Extent1"."MODIFIEDBY_ID");

我无法在代码块中加粗文本，因此请注意Extent限定符在连接中的交换方式。如何在第二个SQL示例中生成它们？

更新

这是我最初在OnModelCreating方法中使用的代码：

modelBuilder.Entity<AppUser>().HasOptional(x => x.CreatedBy).WithOptionalDependent();
modelBuilder.Entity<AppUser>().HasOptional(x => x.ModifiedBy).WithOptionalDependent();

根据回答者的推荐将其更改为：

modelBuilder.Entity<AppUser>().HasOptional(x => x.CreatedBy).WithMany();
modelBuilder.Entity<AppUser>().HasOptional(x => x.ModifiedBy).WithMany();

Answer 1

模型配置有些问题。

我创建了以下课程：

public class AppUser : Entity
{
    public string FirstName { get; set; }
    public string MiddleName { get; set; }
    public string LastName { get; set; }
    public string Identifier { get; set; }
    public bool IsActive { get; set; }
}

将其添加到我的测试DbContext（最新的EF6.1.3）：

public DbSet<AppUser> AppUsers { get; set; }

并且没有任何其他配置出现异常

无法确定类型＆＃39; EFTest.AppUser＆＃39;之间关联的主要结尾。和＆＃39; EFTest.AppUser＆＃39;。必须使用关系流畅API或数据注释显式配置此关联的主要结尾。

所以我在OnModelCreating覆盖中添加了以下内容：

modelBuilder.Entity<AppUser>()
    .HasOptional(e => e.CreatedBy).WithMany();
modelBuilder.Entity<AppUser>()
    .HasOptional(e => e.ModifiedBy).WithMany();

现在迁移成功了。有趣的是，我已经创建了另一个Entity派生实体，并且它不需要这样的配置 - EF正确地确定与上面的配置相同，所以问题似乎是自我引用。

最后，执行以下LINQ查询：

var query = db.AppUsers
    .Select(u => new {  u.FirstName, CreatedBy = u.CreatedBy.FirstName, ModifiedBy = u.ModifiedBy.FirstName })
    .ToList();

按预期生成SQL：

SELECT 
    1 AS [C1], 
    [Extent1].[FirstName] AS [FirstName], 
    [Extent2].[FirstName] AS [FirstName1], 
    [Extent3].[FirstName] AS [FirstName2]
    FROM   [dbo].[AppUsers] AS [Extent1]
    LEFT OUTER JOIN [dbo].[AppUsers] AS [Extent2] ON [Extent1].[CreatedBy_Id] = [Extent2].[Id]
    LEFT OUTER JOIN [dbo].[AppUsers] AS [Extent3] ON [Extent1].[ModifiedBy_Id] = [Extent3].[Id]

很快，请检查您的配置和/或EF版本。

EF6没有按预期生成表连接

1 个答案: