EF的DbContext的单例范围 [英] Singleton Scope for EF's DbContext
问题描述
所以我目前正在使用实体框架的ASP.NET MVC Web应用程序上工作，我也正在使用Ninject进行依赖项注入.
so I am currently working on an ASP.NET MVC web application that uses Entity Framework, I'm also using Ninject for Dependency Injection.
因此，目前基本上，这就是我向Ninject注册我的DbContext和服务的方式.
So basically, at the moment, this is how I register my DbContext and Services with Ninject.
kernel.Bind<DbContext>().To<MyApplicationContext>().InSingletonScope();
kernel.Bind<IAccountService>().To<AccountService>().InSingletonScope();
kernel.Bind<IRegionService>().To<RegionService>().InSingletonScope();
kernel.Bind<IRoleService>().To<RoleService>().InSingletonScope();
我向InSingletonScope注册了它们，这意味着它们将仅创建一次并在应用程序的整个生命周期内使用(至少以我的理解).
I register them with InSingletonScope, which means that they will only be created once and used throughout the lifetime of the application (at least how I understand it).
控制器:
private IAccountService _accountService;
public MemberController(IAccountService accountService)
{
_accountService = accountService;
}
但是，我深感这种单例作用域将在我的Web应用程序中引起问题，尤其是在实体框架的上下文中，因为它是单例的.
However, I have a deep feeling that this singleton scope will cause problem in my web application especially for the Entity Framework's context, due to it being singleton.
因此，我已经遇到了一个小问题，如果我使用SQL Management Studio手动更新数据库，则在我重新启动应用程序之前，Web应用程序的实体框架中的数据将不会更新(似乎是某种缓存机制). EF).
I am already facing a minor issue due to this, if I manually update the database using SQL Management Studio, the data in my web application's Entity Framework wouldn't update until I restart the application (seems to be some caching mechanism in EF).
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但是，如果我删除了InSingletonScope，我会从EF中随机得到错误，说:
However, if I remove the InSingletonScope, I will randomly get errors from EF saying that:
IEntityChangeTracker的多个实例不能引用一个实体对象
An entity object cannot be referenced by multiple instances of IEntityChangeTracker
我理解为什么会这样，因为由AccountService初始化的DbContext可能不同于RegionService.但是我不知道如何解决这个问题.
I understand why this happens because the DbContext initialized by AccountService could be different from say, RegionService. But I have no idea how I can resolve this.
我对依赖注入的理解仍然非常有限，所以任何人都可以请教吗?
My understanding of Dependency Injection is still very limited, so can anybody please advice?
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我已经尝试将所有进样更改为InRequestScope，但是我仍然得到
I've tried changing to InRequestScope for all the injections, but I'm still getting
IEntityChangeTracker的多个实例不能引用一个实体对象
An entity object cannot be referenced by multiple instances of IEntityChangeTracker
当尝试从我的应用程序中的另一服务插入带有相关对象(外键)的新实体时.这意味着他们仍在使用其他DbContext，这是怎么回事?！
When trying to insert a new entity with related object (foreign key) from another service in my application. That means they are still using a different DbContext, what is happening?!
最终好吧，我发现了问题，这是我的缓存机制缓存了先前的请求，导致所有后续请求的关系出现问题.
FINAL Ok I've found the problem, it was my caching mechanism that was caching a previous request, causing the relationship issue on all subsequent request.
推荐答案
我终于设法使用InRequestScope而不是InSingletonScope解决了此问题.
I've finally managed to resolve this issue by using InRequestScope instead of InSingletonScope.
最初，由于我在服务层上已有的缓存机制，在更改为InRequestScope之后，我仍然面临着同样的问题.
Initially, I was still facing the same problem after changing to InRequestScope because of my existing caching mechanism on my services layer.
因此，所有后续请求都使用了最初缓存的实体对象，这就是为什么我从EF收到多个实例错误的原因.
Thus, all subsequent requests were using the initially-cached entity object, that was why I was getting multiple instances error from EF.
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如果您仍然面对着
IEntityChangeTracker的多个实例不能引用一个实体对象
An entity object cannot be referenced by multiple instances of IEntityChangeTracker
更改为InRequestScope后出现
错误，请确保您的实体没有以某种方式缓存或存储以供后续HTTP请求使用.
error after changing to InRequestScope, make sure your entities are not somehow cached or stored for subsequent HTTP requests uses.
这篇关于EF的DbContext的单例范围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！
