Question

我在模型第一种方法中发现了关于在.NET 4.0下运行的EF5的以下问题：我有以下自动生成的实体：

Partial Public Class Notice

    Private _id As Integer
    Public Property id As Integer
        Get
            Return _id
        End Get
        Friend Set(ByVal value As Integer)
            _id = value
        End Set
    End Property
    Public Property order_id As Integer
    Public Property employee_id As Integer
    Public Property sysdate As Datetime
    Public Property content As String

    Public Overridable Property order As Order
    Public Overridable Property employee As Employee

End Class

通知实体通过1（订单，员工）与多个（通知）关系与Order实体和Employee实体相关联。

之后，Order实体还与Employee实体关联：many（Order）to 1（Employee）关系。

然后，我希望以下单元测试失败，因为与Employee实体违规的通知实体关系（我没有指定notice1.employee导航属性）：

<TestMethod()>
    <ExpectedException(GetType(DbUpdateException))>
    Public Sub ShouldNotAllowSaveNoticeWithoutAssignedEmployee()

        Dim notice1 = CreateNewNotice() ' returned entity has not set any relation
        notice1.order= CreateNewOrderWithAllRequiredAndRelatedEntities()

        DbContext.noticeSet.Add(notice1)
        DbContext.SaveChanges()

    End Sub

但结果测试通过了。在数据库中，注意 - ＆gt; employee_id值等于Order-＆gt; employee_id值，这是不期望的，因为这些外键可能指向不同的Employee对象。我本以为我必须自己设置notice1.employee导航属性，如果我忘记了，我想获得DbUpdateException异常。

这种奇怪的EF5行为的原因是什么？

更新

CreateNewNotice()和CreateNewOrderWithAllRequiredAndRelatedEntities()实施：

 Protected Function CreateNewNotice(Optional ByVal suffix As Int32 = 1) As Notice

        Dim notice1 = New Notice() With {
            .sysdate = DateTime.Now,
            .content = Description & suffix ' Description is constant, for testing purposes
        }

        Return notice1 

    End Function

Protected Function CreateNewOrderWithAllRequiredAndRelatedEntities(Optional ByVal suffix As Int32 = 1) As Order

        Dim order1 = CreateNewOrder(suffix) ' returned entity has not set any relation
        order1.employee = CreateNewEmployee(suffix)
        order1.customer = CreateNewCustomerWithAllRequiredRelatedEntities(suffix)
        order1.seller = CreateNewSeller(suffix)

        For i As Integer = 1 To 3
            order1.notices.Add(CreateNewNotice(i)) ' created notices have not initialized relations
        Next

        Return order1

    End Function

Answer 1

我已经认识到这个问题，看起来EF5有不同的行为取决于我们是否使用“外键关联”或“独立关联”（关于EF中关系的一些信息：Relationships and Navigation Properties）< / p>

让我们假设我们使用EF5 Model First Approach（使用.NET 4.5）。让我们考虑自动生成的实体类，与主题问题中出现的示例相关：

Partial Public Class Employee
    Public Property id As Integer
    Public Property firstname As String
    Public Property lastname As String

    Public Overridable Property Notices As ICollection(Of Notice) = New HashSet(Of Notice)
    Public Overridable Property Orders As ICollection(Of Order) = New HashSet(Of Order)

End Class

Partial Public Class Order
    Public Property id As Integer
    Public Property Employee_id As Integer
    Public Property article As String

    Public Overridable Property Notices As ICollection(Of Notice) = New HashSet(Of Notice)
    Public Overridable Property Employee As Employee

End Class

Partial Public Class Notice
    Public Property id As Integer
    Public Property Employee_id As Integer
    Public Property Order_id As Integer
    Public Property sysdate As Date
    Public Property content As String

    Public Overridable Property Employee As Employee
    Public Overridable Property Order As Order

End Class

此实体类使用“外键关联”和“独立关联”。然后，我们有以下单元测试类：

<TestClass()>
Public Class UnitTests

    Protected DbContext As DbModelContext

    <TestInitialize()>
    Public Sub TestInitialize()

        Thread.CurrentThread.CurrentUICulture = New CultureInfo("en-us")
        DbContext = New DbModelContext()

    End Sub

    <TestCleanup()>
    Public Sub TestCleanup()

        DbContext.Dispose()

    End Sub

    <TestMethod()>
    Public Sub Test1()

        Dim notice1 = CreateNewNotice()
        notice1.Order = CreateNewOrderWithAllRequiredAndRelatedEntities()

        DbContext.NoticeSet.Add(notice1)
        DbContext.SaveChanges() ' no DbUpdateException exception

        Assert.AreEqual(notice1.Employee.id, notice1.Order.Employee.id)
        Assert.AreEqual(notice1.Employee.id, notice1.Order.Notices.First().Employee.id)

    End Sub

    <TestMethod()>
    Public Sub Test2()

        Dim notice1 = CreateNewNotice()
        notice1.Order = CreateNewOrderWithAllRequiredAndRelatedEntities()

        DbContext.NoticeSet.Add(notice1)

        Dim employee2 = CreateNewEmployee()

        DbContext.EmployeeSet.Add(employee2)

        DbContext.SaveChanges() 'DbUpdateException exception

    End Sub

    ''' <summary>
    ''' Create new Order object along with required associated objects,
    ''' however related Notice objects do not have assigned required associated objects
    ''' </summary>
    Protected Function CreateNewOrderWithAllRequiredAndRelatedEntities(Optional ByVal suffix As Int32 = 1) As Order

        Dim order1 = CreateNewOrder(suffix)
        order1.Employee = CreateNewEmployee(suffix)

        For i = suffix To suffix + 2

            order1.Notices.Add(CreateNewNotice(i))

        Next

        Return order1

    End Function

    ''' <summary>
    ''' Create new Order object without required associated objects
    ''' </summary>
    Protected Function CreateNewOrder(Optional ByVal suffix As Int32 = 1) As Order

        Dim order1 = New Order() With {
                .article = "article" & suffix
            }

        Return order1

    End Function

    ''' <summary>
    ''' Create new Employee object required without associated objects
    ''' </summary>
    Protected Function CreateNewEmployee(Optional ByVal suffix As Int32 = 1) As Employee

        Dim employee1 = New Employee() With {
                .firstname = "firstname" & suffix,
                .lastname = "lastname" & suffix
            }

        Return employee1

    End Function

    ''' <summary>
    ''' Create new Notice object without associated objects
    ''' </summary>
    Protected Function CreateNewNotice(Optional ByVal suffix As Int32 = 1) As Notice

        Dim notice1 = New Notice() With {
            .sysdate = DateTime.Now,
            .content = "Description" & suffix
        }

        Return notice1

    End Function

End Class

如果我们运行测试，Test1()会通过，但Test2()会失败，但例外情况为：

System.Data.Entity.Infrastructure.DbUpdateException ：无法确定“Model1.NoticeEmployee”关系的主要结尾。多个添加的实体可以具有相同的主键。 ---＆GT; System.Data.UpdateException：无法确定“Model1.NoticeEmployee”关系的主要结尾。多个添加的实体可能具有相同的主键。

结论：

在Test1()内，Employee中只有一个Order个对象和一个DbContext个对象。未在代码中设置的关系（Notice.Employee，Notice.Order）由EF在DbContext.SaveChanges()语句中自动设置。在Test2()内，Employee中有两个DbContext对象，因此Notice.Employee未自动分配值。

奇怪的是，如果我们从模型实体中删除外键属性，为了只具有“独立关联”功能，两个测试都会失败并使用相同的 System.Data.Entity.Infrastructure.DbUpdateException 异常。

同样，如果我们从模型实体中删除导航属性，为了只具有“外键关联”功能，两个测试都会失败并出现相同的异常。

协会奇怪的行为

1 个答案: