实体框架创建空迁移但坚持认为我的模型不同 [英] Entity Framework creates empty migration but insists that my model is different
问题描述
今天是悲伤的一天.今天的第一件事是我看到 EF 异常说支持 'DomainContext' 上下文的模型自数据库创建以来发生了变化.".现在快午夜了，我仍然看到这个错误.我的职业生涯到此结束-(
Today is a sad day. First thing today I saw EF exception saying that "The model backing the 'DomainContext' context has changed since the database was created.". It is close to midnight and I still see this error. This is the end of my career -(
我很确定模型中没有任何变化，但出现了错误.我试过创建一个新的迁移，结果是空的:
I'm pretty sure nothing has changed in the model, yet the error appeared. I have tried creating a new migration, it came out empty:
public void Up()
{
}
public void Down()
{
}
应用此迁移没有任何好处 - 错误仍然存在.我使用了常见的建议将初始化程序设置为空:
Applying this migration did not do any good - the error persisted. I've used common suggestion to set the initialiser to be null:
Database.SetInitializer<DomainContext>(null);
当我访问数据库时，它使错误消失了.但这让我非常困扰 - 每当我尝试通过代码运行迁移时，我都会再次看到类似的错误:
And it made the error go away when I access the database. But this bothers me very much - whenever I try to run migrations through code, I see similar error again:
var configuration = new Migrations.Configuration();
configuration.TargetDatabase = new DbConnectionInfo("correct connection string", "System.Data.SqlClient");
var migrator = new DbMigrator(configuration);
migrator.Update(); // <<-- exception is thrown here
异常抛出如下所示:System.Data.Entity.Migrations.Infrastructure.AutomaticMigrationsDisabledException : 无法更新数据库以匹配当前模型，因为存在待处理的更改并且自动迁移被禁用.将挂起的模型更改写入基于代码的迁移或启用自动迁移.将 DbMigrationsConfiguration.AutomaticMigrationsEnabled 设置为 true 以启用自动迁移.
我已经更新到 EF 6.1(之前是 6.0.2)，但这并没有什么不同.
I've updated to EF 6.1 (was on 6.0.2 before), but this made no difference.
让我困扰的另一件事是我可以通过 Nuget 控制台运行迁移:
Another thing that bothers me that I can run migrations through Nuget Console:
Update-Database
运行良好，没有任何问题.但是当我将数据库初始化程序设置为自动运行迁移时:
Runs fine and does not give any problems. But when I set DB initialiser to run migrations automatically:
var initializer = new MigrateDatabaseToLatestVersion<DomainContext, Migrations.Configuration>();
Database.SetInitializer(initializer);
var domainContext = new DomainContext();
domainContext.Database.Initialize(true); // <<-- this throws exception
无法更新数据库以匹配当前模型，因为存在待处理的更改并且自动迁移已禁用.将挂起的模型更改写入基于代码的迁移或启用自动迁移.将 DbMigrationsConfiguration.AutomaticMigrationsEnabled 设置为 true 以启用自动迁移.
真正的问题是，为什么 EF 在通过 Nuget 控制台和通过 Migrations DB-Initialiser 运行时对模型有不同的哈希值?如何找出不同之处(来自 db-state 的模型)?以及如何解决这个问题，这样我就不必使用 hacks(将 null 分配给 db-initaliser)?
The real question is why does EF has different hashes for models when running through Nuget console and through Migrations DB-Initialiser? How can I find out what is different (model from db-state)? And how to fix this, so I don't have to use hacks (assign null to db-initaliser)?
推荐答案
我的问题的原因是应用于其中一个模型的 [AllowHtml] 属性.在我将 MVC 更新到 5.1.1 并将 WebApi 更新到 2.1 之后，问题就开始发生了.
The cause to my problem was a [AllowHtml] attribute applied to one of the models. The trouble started to happen after I've updated MVC to 5.1.1 and WebApi to 2.1.
我已经从 EF-Model 中删除了该属性，并剥离并重新构建了数据库，问题就消失了.
I've removed that attribute from EF-Model and stripped and re-build the database and the problem was gone.
我写了一篇关于如何调试此类问题的博文:http://tech.trailmax.info/2014/03/inside_of_ef_migrations/
I've written up a blog post on how to debug this kind of problems: http://tech.trailmax.info/2014/03/inside_of_ef_migrations/
另外我认为这个 [AllowHtml] 属性是一个错误，我将创建一个可重现的解决方案并将错误报告提交给 EF-people.
Also I think this [AllowHtml] attribute is a bug, I'll create a reproducible solution and will submit the bug report to EF-people.
更新:我实际上永远无法重现该错误.类属性上的 [AllowHtml] 属性与它无关.这是一个神奇的故障.
Update: I actually could never reproduce the error. [AllowHtml] attribute on class properties had nothing to do with it. A magical glitch that was.
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