asp.net-mvc - 无法使用简单注入(inject)器为每个请求创建 DbContext

Question

尝试注册我的 DbContext 时，简单注入(inject)抛出以下异常。

The supplied connection string is not valid, because it contains insufficient mapping or metadata information. Parameter name: connectionString

我是 DI 新手，可能会遗漏一些相当明显的东西。连接字符串看起来不错。它与通常用于创建 DbContext 的内容相同。我正在尝试解决方案 here

public static class SimpleInjectorInitializer
{
    /// <summary>Initialize the container and register 
    // it as MVC3 Dependency Resolver.</summary>
    public static void Initialize()
    {
        var container = new Container();            
        InitializeContainer(container);
        container.RegisterMvcControllers(
            Assembly.GetExecutingAssembly());            
        container.RegisterMvcAttributeFilterProvider();       
        container.Verify();            
        DependencyResolver.SetResolver(
            new SimpleInjectorDependencyResolver(container));
    }

    private static void InitializeContainer(
        Container container)
    {
    }
}

更新:我仍然没有解决我的问题，但它与 Ninject 的问题非常相似

堆栈跟踪:

System.InvalidOperationException was unhandled by user code
  Message=The configuration is invalid. Creating the instance for type _AccountController failed. Error occurred while trying to get an instance of type _AccountController. The type initializer for 'Web.Controllers._AccountController' threw an exception.
  Source=SimpleInjector
  StackTrace:
       at SimpleInjector.Helpers.Verify(IInstanceProducer instanceProducer, Type serviceType)
       at SimpleInjector.Container.ValidateRegistrations()
       at SimpleInjector.Container.Verify()
       at Web.App_Start.SimpleInjectorInitializer.Initialize() in C:\workspace\BrowsarServer\QARSite\Web\App_Start\SimpleInjectorInitializer.cs:line 24
  InnerException: SimpleInjector.ActivationException
       Message=Error occurred while trying to get an instance of type _AccountController. The type initializer for 'Web.Controllers._AccountController' threw an exception.
       Source=SimpleInjector
       StackTrace:
            at SimpleInjector.InstanceProducers.InstanceProducer.ThrowErrorWhileTryingToGetInstanceOfType(Exception innerException)
            at SimpleInjector.InstanceProducers.InstanceProducer.GetInstance()
            at SimpleInjector.Helpers.Verify(IInstanceProducer instanceProducer, Type serviceType)
       InnerException: System.TypeInitializationException
            Message=The type initializer for 'Web.Controllers._AccountController' threw an exception.
            Source=Web
            TypeName=Web.Controllers._AccountController
            StackTrace:
                 at Web.Controllers._AccountController..ctor()
                 at lambda_method(Closure )
                 at SimpleInjector.InstanceProducers.InstanceProducer.GetInstance()
            InnerException: System.ArgumentException
                 Message=The supplied connection string is not valid, because it contains insufficient mapping or metadata information.
Parameter name: connectionString
                 Source=System.Data.Entity
                 ParamName=connectionString
                 StackTrace:
                      at System.Data.Objects.ObjectContext..ctor(EntityConnection connection, Boolean isConnectionConstructor)
                      at System.Data.Objects.ObjectContext..ctor(String connectionString, String defaultContainerName)
                      at Web.Models.BrowsarEntities..ctor() in C:\workspace\BrowsarServer\QARSite\Web\Models\Browsar.Designer.cs:line 90
                      at Web.Controllers._AccountController..cctor() in C:\workspace\BrowsarServer\QARSite\Web\Controllers\_AccountController.cs:line 15
                 InnerException: System.InvalidOperationException
                      Message=Unable to determine application context. The ASP.NET application path could not be resolved.
                      Source=System.Data.Entity
                      StackTrace:
                           at System.Data.Metadata.Edm.AspProxy.GetBuildManagerReferencedAssemblies()
                           at System.Data.Metadata.Edm.DefaultAssemblyResolver.GetAllDiscoverableAssemblies()
                           at System.Data.Metadata.Edm.DefaultAssemblyResolver.GetWildcardAssemblies()
                           at System.Data.Metadata.Edm.MetadataArtifactLoaderCompositeResource.LoadResources(String assemblyName, String resourceName, ICollection`1 uriRegistry, MetadataArtifactAssemblyResolver resolver)
                           at System.Data.Metadata.Edm.MetadataArtifactLoaderCompositeResource.CreateResourceLoader(String path, ExtensionCheck extensionCheck, String validExtension, ICollection`1 uriRegistry, MetadataArtifactAssemblyResolver resolver)
                           at System.Data.Metadata.Edm.MetadataArtifactLoader.Create(String path, ExtensionCheck extensionCheck, String validExtension, ICollection`1 uriRegistry, MetadataArtifactAssemblyResolver resolver)
                           at System.Data.Metadata.Edm.MetadataCache.SplitPaths(String paths)
                           at System.Data.Common.Utils.Memoizer`2.<>c__DisplayClass2.<Evaluate>b__0()
                           at System.Data.Common.Utils.Memoizer`2.Result.GetValue()
                           at System.Data.Common.Utils.Memoizer`2.Evaluate(TArg arg)
                           at System.Data.EntityClient.EntityConnection.GetMetadataWorkspace(Boolean initializeAllCollections)
                           at System.Data.Objects.ObjectContext.RetrieveMetadataWorkspaceFromConnection()
                           at System.Data.Objects.ObjectContext..ctor(EntityConnection connection, Boolean isConnectionConstructor)
                      InnerException: System.Reflection.TargetInvocationException
                           Message=Exception has been thrown by the target of an invocation.
                           Source=mscorlib
                           StackTrace:
                                at System.RuntimeMethodHandle._InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeType typeOwner)
                                at System.RuntimeMethodHandle.InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, Signature sig, MethodAttributes methodAttributes, RuntimeType typeOwner)
                                at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks)
                                at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
                                at System.Data.Metadata.Edm.AspProxy.GetBuildManagerReferencedAssemblies()
                           InnerException: System.InvalidOperationException
                                Message=This method cannot be called during the application's pre-start initialization stage.
                                Source=System.Web
                                StackTrace:
                                     at System.Web.Compilation.BuildManager.EnsureTopLevelFilesCompiled()
                                     at System.Web.Compilation.BuildManager.GetReferencedAssemblies()
                                InnerException: 

Answer 1

根本原因深埋在内部异常中。当检查堆栈跟踪时，您将能够找到造成这种情况的原因。原因在于以下两个内部异常:

InvalidOperationException: Unable to determine application context. The ASP.NET application path could not be resolved.

和:

InvalidOperationException: This method cannot be called during the application's pre-start initialization stage.

也就是说，这个异常是由于时序问题引起的。我不确定您是否可以更改连接字符串来解决此问题，但您也可以将初始化移至稍后启动应用程序。您可以按如下方式执行此操作:

1. 删除 SimpleInjectorInitializer.cs 类的[程序集:WebActivator.PreApplicationStartMethod](顶行)。
2. 在全局 asax 的 Application_Start() 事件中添加对 SimpleInjectorInitializer.Initialize() 方法的调用。

完成此操作后，对象图的初始化(尤其是验证)是在预初始化状态之后完成的，这对于 ASP.NET 环境中的 EF 来说似乎为时过早。

另一个选择是从 SimpleInjectorInitializer.Initialize 方法中删除 container.Verify(); 调用，因为早期验证过程会害死你。但是，请阅读此Verify the container’s configuration首先，在这样做之前查看替代方案。