c# - 简单注入(inject)器在 Owin 启动期间无法注入(inject)每个 Web API 请求注册类

Question

我正在使用 Owin、Web API、Entity Framework、ASP.NET Identity 创建 API。我正在使用 Simple Injector作为我选择的 DI 框架。

在 Owin 启动过程中，我想用一些样本数据为我的数据库做种。这是由实现 IDatabaseInitializer 的类处理的，它看起来像这样:

public class MyDbInitializer : DropCreateDatabaseAlways<MyDataContext>
{
    private readonly IUserManager _userManager;

    public MyDbInitializer(IUserManager userManager)
    {
        _userManager = userManager;
    }

    protected override void Seed(MyDataContext context)
    {
        SeedIdentities();
    }

    private void SeedIdentities()
    {
        var user = new User
        {
            UserName = "someUsername",
            Email = "some@email.com"
        };

        _userManager.CreateAsync(user, "Password");
    }

IUserManager 是 ASP.NET Identiy UserManager 类的代理，它间接依赖于 IUnitOfWork。如果您想知道，IUserManager 是这样注册的:

container.Register(typeof(IUserManager), 
    () => container.GetInstance<IUserManagerFactory>().Create());

因为我想对每个 Web API 请求使用一个工作单元，所以我注册了我的 IUnitOfWork，如下所示:

container.RegisterWebApiRequest<IUnitOfWork, MyUnitOfWork>();

除了解析 MyDbInitializer 类中的 IUserManager 依赖项之外，这对所有事情都工作得很好。在应用程序启动期间，SimpleInjector 失败并出现以下 ActivationException:

SimpleInjector.ActivationException was unhandled by user code
  HResult=-2146233088
  Message=The registered delegate for type IUserManagerFactory threw an exception. The IUnitOfWork is registered as 'Web API Request' lifestyle, but the instance is requested outside the context of a Web API Request.
   Source=SimpleInjector
   StackTrace:
     at SimpleInjector.InstanceProducer.GetInstance()
     at SimpleInjector.Container.GetInstance[TService]()
     at Project.WebApi.CompositionRoot.SimpleInjectorCompositionRoot.<RegisterSecurityDependencies>b__c() in c:\code\Project\Project.WebApi\CompositionRoot\SimpleInjectorCompositionRoot.cs:line 130
     at lambda_method(Closure )
     at lambda_method(Closure )
     at SimpleInjector.InstanceProducer.GetInstance()
   InnerException: SimpleInjector.ActivationException
     HResult=-2146233088
     Message=The IUnitOfWork is registered as 'Web API Request' lifestyle, but the instance is requested outside the context of a Web API Request.
     Source=SimpleInjector
     StackTrace:
        at SimpleInjector.Scope.GetScopelessInstance[TService,TImplementation](ScopedRegistration`2 registration)
        at SimpleInjector.Scope.GetInstance[TService,TImplementation](ScopedRegistration`2 registration, Scope scope)
        at SimpleInjector.Advanced.Internal.LazyScopedRegistration`2.GetInstance(Scope scope)
        at lambda_method(Closure )
        at SimpleInjector.InstanceProducer.GetInstance()
     InnerException:

我猜 Owin Startup.cs 类被认为在 Web API 请求生命周期之外，并且数据库初始化程序中的构造函数注入(inject)失败，因为它被 Startup 调用。 cs 类。

我不确定如何解决这个问题。我应该使用混合生活方式来注册 IUnitOfWork，还是有更好的解决方案？

Answer 1

你是对的。在启动过程中，没有 Web API 请求。幸运的是，WebApiRequestLifestyle (由 RegisterWebApiRequest 扩展方法使用)使用 ExecutionContextLifestyle在幕后，因此“模拟”网络请求非常简单，如下所示:

// using SimpleInjector.Extensions.ExecutionContextScoping;

using (container.BeginExecutionContextScope())
{
    var initializer = container.GetInstance<MyDbInitializer>();
    intializer.InitializeDatabase();
}