将实体框架移动到MVC中的另一个项目会导致重新迁移 [英] Moving Entity framework to another project from MVC causes re-migration

问题描述

我目前有一个asp.net MVC 4应用程序，其中包含Entity框架6 Code First模型，DbContext和Migrations。为了将其与我的Web应用程序分开，我可以在另一个项目中重新使用这些数据库类，我已将所有相关的实体框架类移动到自己的项目中。

然而，现在当我运行解决方案时，它认为我的模型已经改变，并尝试再运行所有的迁移。这个问题似乎在我使用 SetInitializer ，就像我注释掉这行一样，我可以按照正常的方式运行Web应用程序。

  public static class DatabaseConfig 
 {
 public static void Initialize（）
 {
 System.Data.Entity.Database。 SetInitializer（新的MigrateDatabaseToLatestVersion< G5DataContext，Configuration>（））; 
 
 //确保在SimpleMembership初始化之前创建数据库
使用（var db = new G5DataContext（））
 db.Database.Initialize（true）; 
} 
} 
  

直到我试过移动所有的Entity Framework类。这是不可能的，还是我从根本上做错了？

解决方案

在启动时，EF6查询退出数据库中的迁移，存储在__MigrationHistory表中。该表的一部分是一个上下文键，其中包括实体的命名空间。

如果将所有内容移动到新的命名空间，EF6不会识别以前运行迁移，并尝试重建数据库。

一个快速的解决方案是运行脚本将__MigrationHistory表中的上下文键重命名为新的命名空间。从 http：/ /jameschambers.com/2014/02/changing-the-namespace-with-entity-framework-6-0-code-first-databases/ ：

  UPDATE [dbo]。[__ MigrationHistory] ​​
 SET [ContextKey] ='New_Namespace.Migrations.Configuration'
 WHERE [ContextKey] ='Old_Namespace.Migrations.Configuration' 
  

I currently have an asp.net MVC 4 application which contains Entity framework 6 Code First models, DbContext and Migrations. In an attempt to separate this from my web application so I can re-use these database classes in another project I have moved all related Entity Framework classes to their own project.

However now when I run the solution it thinks my model has changed and attempts to run all my migrations once more. The problem appears to be in my use of SetInitializer as if I comment out this line I can run the web application as per normal.

public static class DatabaseConfig
{
    public static void Initialize()
    {
       System.Data.Entity.Database.SetInitializer(new MigrateDatabaseToLatestVersion<G5DataContext, Configuration>());

        // make sure the database is created before SimpleMembership is initialised
        using (var db = new G5DataContext()) 
            db.Database.Initialize(true);
    }
}

This wasn't a problem until I've tried to move all the Entity Framework classes. Is this not possible, or have I done something fundamentally wrong?

解决方案

At startup, EF6 queries exiting migrations in your database, as stored in the __MigrationHistory table. Part of this table is a context key, which includes the namespace of the entities.

If you move everything to a new namespace, EF6 doesn't recognize any of the previously run migrations, and tries to rebuild the database.

A quick solution is to run a script to rename the context key in the __MigrationHistory table to your new namespace. From http://jameschambers.com/2014/02/changing-the-namespace-with-entity-framework-6-0-code-first-databases/ :

UPDATE [dbo].[__MigrationHistory] 
   SET [ContextKey] = 'New_Namespace.Migrations.Configuration'
 WHERE [ContextKey] = 'Old_Namespace.Migrations.Configuration'

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