由于加入，LINQ to SQL 插入失败

Question

我的数据库中有两个表Users 和HealthMonitor。在HealthMonitor 表中，我有一个UserID 字段映射到Users 表中的ID 字段。

到目前为止非常简单......

我将HealthMonitor 表中的UserID 字段保留为“Nullable”，这样如果没有当前用户登录，我可以让系统将NULL 值插入表中... IE：如果出现错误被抛出给未经身份验证的用户。

问题是当我尝试将 NULL 插入该 UserID 字段时插入失败。

仅供参考：删除关系也可以解决问题，但我知道这可能不是完成任务的最佳方式

编辑：

在重新应用关系并确保 UserID 可以为空后，它现在似乎可以工作了...但是该值插入为 0 而不是 null

    Public Sub AddException(ByVal ex As Exception, Optional ByVal notes As String = Nothing) Implements IHealthMonitorService.AddException
        Dim exception As HealthMonitor = New HealthMonitor
        Dim userID As Integer = Nothing
        If HttpContext.Current.User.Identity.IsAuthenticated Then userID = Authentication.CustomAuthentication.RetrieveAuthUser.ID

        Dim DataConverter As Utilities.DataConverters = New Utilities.DataConverters
        Dim InformationHelper As Utilities.InformationHelper = New Utilities.InformationHelper

        With exception
            .DateTime = DateTime.Now
            .Exception = ex.ToString
            .Message = ex.Message
            .Notes = notes
            .ShortMessage = If(ex.Message.Length > 50, ex.Message.Substring(0, 50), ex.Message)
            .Source = ex.Source
            .StackTrace = ex.StackTrace
            .Url = HttpContext.Current.Request.Url.ToString()
            .UserID = userID
            .UserIP = DataConverter.IPAddressToNumber(InformationHelper.GetUserIP)
            .UserOS = InformationHelper.GetUserOS()
            .UserBrowser = InformationHelper.GetUserBrowser()
        End With

        _HealthMonitorRepository.AddException(exception)
    End Sub

我在这里遗漏了什么吗？可以插入为NULL

编辑：

好吧，所以我撒了一点谎。我仍然收到错误

    Public Sub AddException(ByVal exception As HealthMonitor) Implements IHealthMonitorRepository.AddException
        dc.HealthMonitors.InsertOnSubmit(exception)
        dc.SubmitChanges()  ''# ERROR HERE
    End Sub

INSERT 语句与 FOREIGN KEY 约束“FK_un_HealthMonitor_un_Users”冲突。冲突发生在数据库“UrbanNow”、表“dbo.un_Users”、列“ID”中。 声明已终止。

这是桌子

/****** Object:  Table [dbo].[un_HealthMonitor]    Script Date: 07/24/2010 10:48:39 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[un_HealthMonitor](
    [ID] [int] IDENTITY(1,1) NOT NULL,
    [UserID] [int] NULL,
    [Exception] [nvarchar](4000) NULL,
    [Url] [nvarchar](2048) NULL,
    [Source] [nvarchar](4000) NULL,
    [ShortMessage] [nvarchar](50) NULL,
    [Message] [nvarchar](4000) NULL,
    [StackTrace] [nvarchar](4000) NULL,
    [UserIP] [nvarchar](50) NULL,
    [UserBrowser] [nvarchar](50) NULL,
    [UserOS] [nvarchar](50) NULL,
    [UserIsMoblie] [bit] NULL,
    [DateTime] [datetime2](0) NULL,
    [Notes] [nvarchar](4000) NULL,
 CONSTRAINT [PK_un_HealthMonitor] 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].[un_HealthMonitor]  WITH CHECK ADD  CONSTRAINT [FK_un_HealthMonitor_un_Users] FOREIGN KEY([UserID])
REFERENCES [dbo].[un_Users] ([ID])
GO

ALTER TABLE [dbo].[un_HealthMonitor] CHECK CONSTRAINT [FK_un_HealthMonitor_un_Users]
GO

Answer 1

成功了！！！

所以基本上在我的服务层中我有......

    Public Sub AddException(ByVal ex As Exception, Optional ByVal notes As String = Nothing) Implements IHealthMonitorService.AddException
        Dim exception As HealthMonitor = New HealthMonitor
        Dim userID As Integer = Nothing
        If HttpContext.Current.User.Identity.IsAuthenticated Then userID = Authentication.CustomAuthentication.RetrieveAuthUser.ID

        Dim DataConverter As Utilities.DataConverters = New Utilities.DataConverters
        Dim InformationHelper As Utilities.InformationHelper = New Utilities.InformationHelper

        With exception
            .DateTime = DateTime.Now
            .Exception = ex.ToString
            .Message = ex.Message
            .Notes = notes
            .ShortMessage = If(ex.Message.Length > 50, ex.Message.Substring(0, 50), ex.Message)
            .Source = ex.Source
            .StackTrace = ex.StackTrace
            .Url = HttpContext.Current.Request.Url.ToString()
            .UserID = userID
            .UserIP = DataConverter.IPAddressToNumber(InformationHelper.GetUserIP)
            .UserOS = InformationHelper.GetUserOS()
            .UserBrowser = InformationHelper.GetUserBrowser()
        End With

        _HealthMonitorRepository.AddException(exception)
    End Sub

问题在于，当我将userID 发送到异常对象时，它正在向数据库发送0（零）。这是解决方案

        Dim userID As Integer? = Nothing ''# (?) makes the integer nullable.

Answer 2

为确保您有一个用户并因此不违反外键，您可以执行以下操作：

`Public Sub AddException(ByVal exception As HealthMonitor) Implements IHealthMonitorRepository.AddException
    ' take what you need from exception to Create a User
    User user = new User{Populate properties here}
    dc.Users.InsertOnSubmit(user)   
    dc.HealthMonitors.InsertOnSubmit(exception)
    dc.SubmitChanges()  ''# ERROR HERE
End Sub'

如果需要，您可以通过这种方式创建用户。

或者您可以为用户进行存在性检查。