属性上的 ForeignKeyAttribute 无效

Question

我已阅读How Should I Declare Foreign Key Relationships Using Code First Entity Framework (4.1) in MVC3?，但我无法接到电话以产生任何结果。它有以下错误：

类型上的属性“Footer_Item_Header_ID”上的 ForeignKeyAttribute “MyBlog.Tbl_Footer_Item”无效。导航属性 在依赖类型上找不到“Tbl_Footer_Header” 'MyBlog.Tbl_Footer_Item'。 Name 值应该是有效的导航 属性名称。

在这一行：

Dim footerNavElements = db.Tbl_Footer_Headers.Where(Function(i) i.Footer_Header_Order = 1).Single.Items

这是我的父模型：

Imports System.Data.Entity
Imports System.ComponentModel.DataAnnotations

Public Class Tbl_Footer_Header

    <Key()> Public Property Footer_Header_ID() As Integer
    Public Property Footer_Header_Content() As String
    Public Property Footer_Header_Order() As Integer

    Public Overridable Property Items As ICollection(Of Tbl_Footer_Item)

End Class

Public Class FooterHeaderDbContext
    Inherits DbContext

    Public Property Tbl_Footer_Headers As DbSet(Of Tbl_Footer_Header)

End Class

这是我的孩子模型：

Imports System.Data.Entity
Imports System.ComponentModel.DataAnnotations

Public Class Tbl_Footer_Item

    <Key()> Public Property Footer_Item_ID() As Integer
    <ForeignKey("Tbl_Footer_Header")>
    Public Property Footer_Item_Header_ID() As Integer
    Public Property Footer_Item_Content() As String
    Public Property Footer_Item_Link() As String
    Public Property Footer_Header_Order() As Integer

    Public Overridable Property Header As Tbl_Footer_Header

End Class

Public Class FooterItemDbContext
    Inherits DbContext

    Public Property Tbl_Footer_Items As DbSet(Of Tbl_Footer_Item)
    Public Property Tbl_Footer_Headers As DbSet(Of Tbl_Footer_Header)

End Class

我该怎么做才能使操作产生没有错误的结果？谢谢。

Answer 1

你的外键注解应该是属性的名称，而不是类型。

您的导航属性是 Header:

Public Overridable Property Header As Tbl_Footer_Header

所以你的注释，应该引用该属性。将其更改为：

<ForeignKey("Header")>
Public Property Footer_Item_Header_ID() As Integer