C# 为什么实体框架（带有RIA服务）在子记录不'；不存在？

实体框架4排除了我认为不应该出现的记录。以下是我的设想：

表定义

Table_1

    UniqueIdentifier ID not null
    int AnotherField

Table_2

    UniqueIdentifier ID not null
    UniqueIdentifier Table_1ID not null
    int Priority not null

表1和表2之间通过表ID字段存在关系。它是在数据库中定义的，实体框架可以识别它

我在DomainService中定义了一个查询：

private ObjectQuery<Table_1> Table_1WithIncludes()    
{        
    return this.ObjectContext.Table_1        
        .Include("Table_2")                
}

因此，从本质上讲，如果表2中的优先级字段为null（当表2中没有与父表Tabe_1对应的记录时），where子句会导致两个记录都退出（null>0失败）

现在，如果我更改优先级字段的定义，使其不再是必需的，它将消除强制转换和检查，一切都很好。但看起来我不该这么做

我做错什么了吗？我的理解有问题吗？

完整的EntityQuery和生成的查询文本如有帮助，请参见下文

    private ObjectQuery<Event> EventsWithIncludes()
    {
        return this.ObjectContext.Events
            .Include("Place")
            .Include("EventInvitees")
            .Include("EventInvitees.User");
    }


exec sp_executesql N'SELECT 
[Project2].[NumberOfPeople] AS [NumberOfPeople], 
[Project2].[ID] AS [ID], 
[Project2].[CreatorID] AS [CreatorID], 
[Project2].[CreateDate] AS [CreateDate], 
[Project2].[PlacesID] AS [PlacesID], 
[Project2].[EventDate] AS [EventDate], 
[Project2].[EventTime] AS [EventTime], 
[Project2].[Availability] AS [Availability], 
[Project2].[EscalationLevels] AS [EscalationLevels], 
[Project2].[Rank] AS [Rank], 
[Project2].[RowVersion] AS [RowVersion], 
[Project2].[ID1] AS [ID1], 
[Project2].[Name] AS [Name], 
[Project2].[Phone] AS [Phone], 
[Project2].[DefaultPar] AS [DefaultPar], 
[Project2].[DefaultSlope] AS [DefaultSlope], 
[Project2].[DefaultRating] AS [DefaultRating], 
[Project2].[CreateDate1] AS [CreateDate1], 
[Project2].[UpdateDate] AS [UpdateDate], 
[Project2].[MetroAreaID] AS [MetroAreaID], 
[Project2].[C1] AS [C1], 
[Project2].[PriorityOrder] AS [PriorityOrder], 
[Project2].[ID2] AS [ID2], 
[Project2].[EventsID] AS [EventsID], 
[Project2].[InviteeUsersID] AS [InviteeUsersID], 
[Project2].[RowVersion1] AS [RowVersion1], 
[Project2].[Attending] AS [Attending], 
[Project2].[StatusChange] AS [StatusChange], 
[Project2].[ID3] AS [ID3], 
[Project2].[First] AS [First], 
[Project2].[Last] AS [Last], 
[Project2].[UserName] AS [UserName], 
[Project2].[Password] AS [Password], 
[Project2].[Gender] AS [Gender], 
[Project2].[Email] AS [Email], 
[Project2].[Email_Sharing] AS [Email_Sharing], 
[Project2].[Email_Receive] AS [Email_Receive], 
[Project2].[Phone1] AS [Phone1], 
[Project2].[Phone_Sharing] AS [Phone_Sharing], 
[Project2].[Phone_Receive] AS [Phone_Receive], 
[Project2].[CreateDate2] AS [CreateDate2], 
[Project2].[UpdateDate1] AS [UpdateDate1]
FROM ( SELECT 
    [Project1].[ID] AS [ID], 
    [Project1].[CreatorID] AS [CreatorID], 
    [Project1].[CreateDate] AS [CreateDate], 
    [Project1].[NumberOfPeople] AS [NumberOfPeople], 
    [Project1].[PlacesID] AS [PlacesID], 
    [Project1].[EventDate] AS [EventDate], 
    [Project1].[Availability] AS [Availability], 
    [Project1].[EscalationLevels] AS [EscalationLevels], 
    [Project1].[Rank] AS [Rank], 
    [Project1].[RowVersion] AS [RowVersion], 
    [Project1].[EventTime] AS [EventTime], 
    [Extent3].[ID] AS [ID1], 
    [Extent3].[Name] AS [Name], 
    [Extent3].[Phone] AS [Phone], 
    [Extent3].[DefaultPar] AS [DefaultPar], 
    [Extent3].[DefaultSlope] AS [DefaultSlope], 
    [Extent3].[DefaultRating] AS [DefaultRating], 
    [Extent3].[CreateDate] AS [CreateDate1], 
    [Extent3].[UpdateDate] AS [UpdateDate], 
    [Extent3].[MetroAreaID] AS [MetroAreaID], 
    [Join2].[ID1] AS [ID2], 
    [Join2].[EventsID] AS [EventsID], 
    [Join2].[InviteeUsersID] AS [InviteeUsersID], 
    [Join2].[PriorityOrder] AS [PriorityOrder], 
    [Join2].[RowVersion] AS [RowVersion1], 
    [Join2].[Attending] AS [Attending], 
    [Join2].[StatusChange] AS [StatusChange], 
    [Join2].[ID2] AS [ID3], 
    [Join2].[First] AS [First], 
    [Join2].[Last] AS [Last], 
    [Join2].[UserName] AS [UserName], 
    [Join2].[Password] AS [Password], 
    [Join2].[Gender] AS [Gender], 
    [Join2].[Email] AS [Email], 
    [Join2].[Email_Sharing] AS [Email_Sharing], 
    [Join2].[Email_Receive] AS [Email_Receive], 
    [Join2].[Phone] AS [Phone1], 
    [Join2].[Phone_Sharing] AS [Phone_Sharing], 
    [Join2].[Phone_Receive] AS [Phone_Receive], 
    [Join2].[CreateDate] AS [CreateDate2], 
    [Join2].[UpdateDate] AS [UpdateDate1], 
    CASE WHEN ([Join2].[PriorityOrder] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C1]
    FROM    (SELECT 
        [Extent1].[ID] AS [ID], 
        [Extent1].[CreatorID] AS [CreatorID], 
        [Extent1].[CreateDate] AS [CreateDate], 
        [Extent1].[NumberOfPeople] AS [NumberOfPeople], 
        [Extent1].[PlacesID] AS [PlacesID], 
        [Extent1].[EventDate] AS [EventDate], 
        [Extent1].[Availability] AS [Availability], 
        [Extent1].[EscalationLevels] AS [EscalationLevels], 
        [Extent1].[Rank] AS [Rank], 
    [Extent1].[RowVersion] AS [RowVersion], 
    [Extent1].[EventTime] AS [EventTime], 
    (SELECT 
        COUNT(1) AS [A1]
        FROM [dbo].[EventInvitees] AS [Extent2]
        WHERE ([Extent1].[ID] = [Extent2].[EventsID]) AND ([Extent2].[InviteeUsersID] = @p__linq__2)) AS [C1]
    FROM [dbo].[Events] AS [Extent1] ) AS [Project1]
LEFT OUTER JOIN [dbo].[Places] AS [Extent3] ON [Project1].[PlacesID] = [Extent3].[ID]
LEFT OUTER JOIN  (SELECT [Extent4].[ID] AS [ID1], [Extent4].[EventsID] AS [EventsID], [Extent4].[InviteeUsersID] AS [InviteeUsersID], [Extent4].[PriorityOrder] AS [PriorityOrder], [Extent4].[RowVersion] AS [RowVersion], [Extent4].[Attending] AS [Attending], [Extent4].[StatusChange] AS [StatusChange], [Extent5].[ID] AS [ID2], [Extent5].[First] AS [First], [Extent5].[Last] AS [Last], [Extent5].[UserName] AS [UserName], [Extent5].[Password] AS [Password], [Extent5].[Gender] AS [Gender], [Extent5].[Email] AS [Email], [Extent5].[Email_Sharing] AS [Email_Sharing], [Extent5].[Email_Receive] AS [Email_Receive], [Extent5].[Phone] AS [Phone], [Extent5].[Phone_Sharing] AS [Phone_Sharing], [Extent5].[Phone_Receive] AS [Phone_Receive], [Extent5].[CreateDate] AS [CreateDate], [Extent5].[UpdateDate] AS [UpdateDate]
    FROM  [dbo].[EventInvitees] AS [Extent4]
    INNER JOIN [dbo].[Users] AS [Extent5] ON [Extent4].[InviteeUsersID] = [Extent5].[ID] ) AS [Join2] ON [Project1].[ID] = [Join2].[EventsID]
WHERE ([Project1].[C1] > 0) AND ([Project1].[CreatorID] = @p__linq__0) AND (([Project1].[EventDate] IS NULL) OR ([Project1].[EventDate] >= @p__linq__1))
)  AS [Project2]
ORDER BY [Project2].[ID] ASC, [Project2].[ID1] ASC, [Project2].[C1] ASC',N'@p__linq__2     uniqueidentifier,@p__linq__0 uniqueidentifier,@p__linq__1 datetime2(7)',@p__linq__2='33BB8199-7B25-4B3A-B96D-044EB7DB70AE',@p__linq__0='33BB8199-7B25-4B3A-B96D-044EB7DB70AE',@p__linq__1='1900-01-01 00:00:00'

---

如果您的外键是非空的，那么根据EF，您的关系是一对多的，有些每个子级都必须有父级。所以从理论上讲，没有父母你就不能有孩子

---

如果您希望有没有父级的子级，那么您的关系是零或一对多，并且您的外键应该可以为null

我所看到的实体框架单个

Include

总是转换为外部连接。但是，对于多个包含，包含的顺序决定了连接是内部的还是外部的

在您的示例中，我假设“Place”是外部连接的，而“eventinvites”和“User”都是内部连接的。（至少当我进行类似的查询时会发生这种情况）

如果你能把订单改成

.Include("EventInvitees")
.Include("EventInvitees.User")
.Include("Place")

“Place”是内部连接的，“eventinvites”是外部连接的（同样，基于我的类似案例）

---

我在MSDN上找不到任何关于此操作的确切逻辑的文档，因此您的结果可能与我的不同。

这真的是实体框架的工作方式吗？在我所做的几乎所有的专业工作中，总是存在这样的情况：你有父母记录（如人口统计）而没有子女记录（如地址）。我发现很难相信，为了解释这种情况，实体框架会要求我们允许外键中始终应提供的空值。这伤害了我的核心，如果这种类型的违反是意料之中的。你确定这是正确的吗？你在什么地方看到文档了吗？你可以有没有子表的父表，但不能有没有父表的子表。不……实际上，如果你在第一个大代码块中向下滚动，你可以看到所有表都是外部联接的（用户表除外，该表未特别包括，但使用实体模型上的属性来实现）.我尝试颠倒顺序，但没有帮助。添加了相同的筛选器。啊，是的，忽略了那个筛选器。我们似乎在这里留下了尝试和错误，这有点令人沮丧。是的……我可以绕过它，但要做到这一点，我必须违反要求优先级的业务规则的实施。我可以在客户端强制执行，但不能事情变得一团糟。只是想找一个更好的方法。不过感谢您的关注。在linq中手动编写联接、内部联接的联接和外部联接的GroupJoin可能会更成功。我认为EF不会为这些添加自己的逻辑。

USE [TheGreen18]
GO

/****** Object:  Table [dbo].[EventInvitees]    Script Date: 03/17/2012 22:27:16 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[EventInvitees](
    [ID] [uniqueidentifier] NOT NULL,
    [EventsID] [uniqueidentifier] NOT NULL,
    [InviteeUsersID] [uniqueidentifier] NOT NULL,
    [PriorityOrder] [int] NOT NULL,
    [RowVersion] [timestamp] NULL,
    [Attending] [bit] NULL,
    [StatusChange] [datetime] NULL,
 CONSTRAINT [PK_EventInvitees] PRIMARY KEY CLUSTERED 
(
    [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].[EventInvitees]  WITH CHECK ADD  CONSTRAINT [FK_EventInvitees_Events] FOREIGN KEY([EventsID])
REFERENCES [dbo].[Events] ([ID])
ON DELETE CASCADE
GO

ALTER TABLE [dbo].[EventInvitees] CHECK CONSTRAINT [FK_EventInvitees_Events]
GO

ALTER TABLE [dbo].[EventInvitees]  WITH CHECK ADD  CONSTRAINT [FK_EventInvitees_Users] FOREIGN KEY([InviteeUsersID])
REFERENCES [dbo].[Users] ([ID])
GO

ALTER TABLE [dbo].[EventInvitees] CHECK CONSTRAINT [FK_EventInvitees_Users]
GO

.Include("EventInvitees")
.Include("EventInvitees.User")
.Include("Place")