实体框架 6 - 缺少仅具有引用不同表的主键的表 [英] Entity Framework 6 - Missing table with only primary keys referencing different tables

问题描述

随着我们远离 Linq2Sql，我们正在学习 Entity Framework 6.1(来自 NuGet).我们有一小部分表将两个单独的表关联起来，如下所示.

We are learning Entity Framework 6.1 (from NuGet) as we move away from Linq2Sql. We have a small handful of tables that associate two separate tables like shown below.

EF6 数据库第一代

数据库图:

架构概览:

在 Visual Studio 中，空白类库，执行 Database First EF6 EDMX 文件时，图表仅生成 TableA 和 TableC - TableB 不会生成.

When in Visual studios, blank class library, doing a Database First EF6 EDMX file, the diagram only generates TableA and TableC -- the TableB does not get generated.

Visual Studio 视图:

Visual Studios View:

可以看到只创建了 TableA 和 TableC.从技术上讲，应该已经创建了 TableB，因为您希望能够管理这些引用.

You can see that only TableA and TableC are created. Technically TableB should have been created, because you would want to be able to manage those references.

图中A和C的关联关系:

The Association between A and C shown in the diagram:

我觉得我错过了一个选项，或者误解了实体框架的一个关键概念.知道如何使用 T4 生成丢失的 TableB 吗?EDMX 文件确实显示了它，但由于某种原因，它没有生成到具有两个属性的 .CS 文件中.

I feel like I am missing an option, or misunderstanding a key concept of Entity Framework. Any idea how to have the missing TableB generated with the T4? The EDMX file does show it, but for some reason it doesn't get generated into a .CS file with the two properties indicating the relationship.

我们需要这个的主要原因是我们扩展了 EF6 T4 模板以添加一些工厂模式以匹配我们现有的模型.因为它没有为 TableB 生成一个类，所以我们没有得到我们正在寻找的自动生成的代码.

The primary reason we need this, is we extended the EF6 T4 template to add some factory patterns to match our existing models. Because it doesnt generate a class for TableB, we dont get the autogenerated code that we are looking for.

想法/建议?谢谢.

推荐答案

EF不会生成弱实体或连接表，需要通过fluent API或使用数据注释手动配置关系

Weak entities or join tables will not be generated by EF, you need to configure the relationships manually thru fluent API or using data annotations

如微软网站所述:根据关系约定:

As stated on Microsoft's website: under Relationship's convention:

注意:如果您在相同类型之间有多个关系(例如例如，假设您定义了 Person 和 Book 类，其中Person 类包含 ReviewedBooks 和 AuthoredBooks 导航属性和 Book 类包含 Author 和 Reviewer导航属性)，您需要手动配置通过使用 Data Annotations 或 fluent API 建立关系.更多信息，请参阅数据注释 - 关系和 Fluent API -关系.

Note: If you have multiple relationships between the same types (for example, suppose you define the Person and Book classes, where the Person class contains the ReviewedBooks and AuthoredBooks navigation properties and the Book class contains the Author and Reviewer navigation properties) you need to manually configure the relationships by using Data Annotations or the fluent API. For more information, see Data Annotations - Relationships and Fluent API - Relationships.

有关详细信息，请参阅此链接

Refer to this link for more information

更新

以下解决方法适用于 EDMX(但需要维护):

A workaround will work in case of EDMX ( but it cost maintenance) as follows:

1. 从数据库中的连接表中删除外键
2. 从数据库更新 EDMX
3. 在连接表中重新创建外键

只要您不再从数据库中更新您的模型，此解决方法就会起作用.

this workaround will work as long as you will not update your Model from the database again.

推荐的解决方案，保留由 EDMX 生成的所有内容，并使用用户@TravisWhidden"报告为有用"的以下链接详细了解如何在此案例中使用 crud 操作

Recommended solution, keep everything as it was generated by EDMX and learn more about how to use crud operation for this case using the following links that were reported "helpful" by the user '@TravisWhidden'

1. 插入/更新多对多实体框架.我该怎么做?
2. https://www.youtube.com/watch?v=uMQwORSTGX4(视频)

这篇关于实体框架 6 - 缺少仅具有引用不同表的主键的表的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！