ef-code-first - EF Code First 向查询添加了额外的列，该列不再存在于模型中

Question

这是我关于 SO 的第一个问题。

我有一个 ASP.NET 4.0 MVC3 项目，它使用 EF Code First 作为 ORM 和 FluentMigrator 进行版本迁移。我有 Message 实体类，如下所示:

public class Message
{
    [Key]
    [Column("Message_Id")]
    public int Id { get; set; }

    public DateTime CreatedTime { get; set; }

    [Required]
    [StringLength(MaxSubjectLength)]
    public string Subject { get; set; }

    [Required]
    [StringLength(MaxBodyLength)]
    public string Body { get; set; }

    public Link Link { get;set; }
}

未定义自定义映射，以及 MSSQL Server 2012 数据库表消息:

CREATE TABLE [dbo].[Messages](
    [Message_Id] [int] IDENTITY(1,1) NOT NULL,
    [CreatedTime] [datetime] NOT NULL,
    [Subject] [nvarchar](78) NOT NULL,
    [BodyHtml] [nvarchar](2000) NOT NULL,
    [Link_Id] [int] NULL,
    [Collection_Id] [int] NULL,
    [MessageType] [nvarchar](30) NOT NULL,
 CONSTRAINT [PK_Messages] PRIMARY KEY CLUSTERED 
(
    [Message_Id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

GO

ALTER TABLE [dbo].[Messages]  WITH CHECK ADD  CONSTRAINT [FK_Messages_Collection] FOREIGN KEY([Collection_Id])
REFERENCES [dbo].[Collections] ([Id])
GO

ALTER TABLE [dbo].[Messages] CHECK CONSTRAINT [FK_Messages_Collection]
GO

ALTER TABLE [dbo].[Messages]  WITH CHECK ADD  CONSTRAINT [FK_Messages_Link] FOREIGN KEY([Link_Id])
REFERENCES [dbo].[Links] ([Id])
GO

ALTER TABLE [dbo].[Messages] CHECK CONSTRAINT [FK_Messages_Link]
GO

Link_Id、Collection_Id 和 MessageType 列在该表中，因为我想做 TPH 继承(实际上我想做 TPT 继承，然后切换到 TPH，我猜它会解决我的问题，但没有)。

现在我想要 LinkMessage 和 CollectionMessage 类应该是这样的:

public class LinkMessage : Message
{
    public int? Link_Id { get;set; }
}

public class CollectionMessage : Message
{
    public int? Collection_Id { get;set; }
}

所以问题是: 即使没有定义继承(即只有消息实体存在)，当我删除链接导航属性，重建我的项目，(甚至重新创建数据库等)并做简单的查询 var a = DBContext.Messages.ToList();EF 生成以下查询:

SELECT 
[Extent1].[Message_Id] AS [Message_Id], 
[Extent1].[CreatedTime] AS [CreatedTime], 
[Extent1].[Subject] AS [Subject], 
[Extent1].[BodyHtml] AS [BodyHtml], 
[Extent1].[Link_Id] AS [Link_Id]
FROM [dbo].[Messages] AS [Extent1]

为什么它仍然包含Link_Id？它不在模型中了。这将导致继承问题 - 当我使用上面的子类进行 TPH(或 TPT)继承时，应用程序失败并显示错误“无效的列名 'Link_Id1'”。为什么是 Link_Id1？这怎么会发生？我完全糊涂了。 'Collection_Id' 列表现正常。这两列是相同的。 我试图 重新创建数据库，杀死了应用程序的所有进程(甚至重新启动了我的电脑)，尝试加载以前的修订版并在那里删除 Message.Link_Id 属性，尝试使用数据但没有相同的行为。我试图用谷歌搜索一些东西，但最终一无所获，因为实际上我什至不知道如何进行正确的搜索查询，而我所做的搜索却没有给我任何东西，我正在用它度过第二天......

以下是它们生成的查询和 SQL:

var b = DBContext.Messages.OfType<CollectionMessage>();

SELECT 
[Extent1].[Message_Id] AS [Message_Id], 
'0X0X' AS [C1], 
[Extent1].[CreatedTime] AS [CreatedTime], 
[Extent1].[Subject] AS [Subject], 
[Extent1].[BodyHtml] AS [BodyHtml], 
[Extent1].[Collection_Id] AS [Collection_Id], 
[Extent1].[Link_Id1] AS [Link_Id1]
FROM [dbo].[Messages] AS [Extent1]
WHERE [Extent1].[MessageType] = N'CollectionMessage'


var b = DBContext.Messages.OfType<LinkMessage>();

SELECT 
[Extent1].[Message_Id] AS [Message_Id], 
'0X0X' AS [C1], 
[Extent1].[CreatedTime] AS [CreatedTime], 
[Extent1].[Subject] AS [Subject], 
[Extent1].[BodyHtml] AS [BodyHtml], 
[Extent1].[Link_Id] AS [Link_Id], 
[Extent1].[Link_Id1] AS [Link_Id1]
FROM [dbo].[Messages] AS [Extent1]
WHERE [Extent1].[MessageType] = N'LinkMessage'


var b = DBContext.Messages;

SELECT 
[Extent1].[Message_Id] AS [Message_Id], 
CASE WHEN (((CASE WHEN ([Extent1].[MessageType] = N'LinkMessage') THEN cast(1 as bit) ELSE cast(0 as bit) END) <> cast(1 as bit)) AND ((CASE WHEN ([Extent1].[MessageType] = N'CollectionMessage') THEN cast(1 as bit) ELSE cast(0 as bit) END) <> cast(1 as bit))) THEN '0X' WHEN ([Extent1].[MessageType] = N'LinkMessage') THEN '0X0X' ELSE '0X1X' END AS [C1], 
[Extent1].[CreatedTime] AS [CreatedTime], 
[Extent1].[Subject] AS [Subject], 
[Extent1].[BodyHtml] AS [BodyHtml], 
CASE WHEN (((CASE WHEN ([Extent1].[MessageType] = N'LinkMessage') THEN cast(1 as bit) ELSE cast(0 as bit) END) <> cast(1 as bit)) AND ((CASE WHEN ([Extent1].[MessageType] = N'CollectionMessage') THEN cast(1 as bit) ELSE cast(0 as bit) END) <> cast(1 as bit))) THEN CAST(NULL AS int) WHEN ([Extent1].[MessageType] = N'LinkMessage') THEN [Extent1].[Link_Id] END AS [C2], 
CASE WHEN (((CASE WHEN ([Extent1].[MessageType] = N'LinkMessage') THEN cast(1 as bit) ELSE cast(0 as bit) END) <> cast(1 as bit)) AND ((CASE WHEN ([Extent1].[MessageType] = N'CollectionMessage') THEN cast(1 as bit) ELSE cast(0 as bit) END) <> cast(1 as bit))) THEN CAST(NULL AS int) WHEN ([Extent1].[MessageType] = N'LinkMessage') THEN CAST(NULL AS int) ELSE [Extent1].[Collection_Id] END AS [C3], 
[Extent1].[Link_Id1] AS [Link_Id1]
FROM [dbo].[Messages] AS [Extent1]

为什么查询 Link_Id 和 Link_Id1 列？请有人帮助我，我错过了什么？

UPD: 当我删除自定义 DBInitializer 并让 Code First 为我创建 DB 时，它会在“消息”表中创建额外的列“Link_Id1”。

Answer 1

抱歉各位，我知道这应该是一些愚蠢的小错误，但没想到会这么愚蠢。实际上 Link 实体中包含 Messages 的集合。这个属性没有被经常使用，所以我们在其他属性中没有注意到它。当我删除它时 - 一切都开始工作了。

所以它开始是一个非常有趣的问题，但最终得到 非常明显的答案 - 人为因素 。

对于所有刚接触 EF 并且落入同一个洞穴的人，我会留下一个说明:EF 无法“记住”某些属性，除非它引用了它。因此，如果您确实遇到类似的麻烦，请仔细检查您的代码并请其他人来做，这没有什么神奇之处!

我现在无法投票，所以 soadyp , Gert Arnold - 感谢您的帮助!