c# - Autofac 未解析 ApiController 的类型和命名参数

Question

我有三个不同的应用程序，它们都使用相同的业务层/数据层构建。我将 IUserNameProvider 添加到所有三个应用程序使用的 IUnitOfWork 类。因为每个应用程序使用不同的方法获取用户名，所以我创建了 IUserNameProvider 并使用 Autofac 注入(inject)适当的实现。

这看起来应该是相当简单的代码，但我无法为 Web API 应用程序正确配置它。类似的代码在控制台应用程序中运行良好

我的 Global.asax.cs

protected void Application_Start()
{
    var builder = new ContainerBuilder();

    builder.RegisterType<WebAPIGetUser>().As<SSEMPA.DataAccess.Infrastructure.IUserNameProvider>();
    builder.RegisterType<UnitOfWork>().As<IUnitOfWork>()
     .WithParameter("connectionString", ConfigurationManager.ConnectionStrings["MyDataContex"].ConnectionString);

    //other type registrations ...

    DependencyResolver.SetResolver(new AutofacDependencyResolver(builder.Build()));

    // other registrations ....
}

我的 UnitOfWork 构造函数

public class UnitOfWork : IUnitOfWork
{
    private MyDataContext dataContext;

    public UnitOfWork(IUserNameProvider userNameProvider, string connectionString)
    {
        dataContext = new MyDataContext (connectionString, userNameProvider);
    }

    ...
}

我的 API Controller

public class AgencyApiController : ApiController
{
    private readonly IUnitOfWork _unitOfWork;

    public AgencyApiController(IUnitOfWork unitOfWork)
    {
        _unitOfWork = unitOfWork;
    }

    ...
}

当 API 被命中时，它会抛出以下错误:

<Error>
    <Message>An error has occurred.</Message>
    <ExceptionMessage>An error occurred when trying to create a controller of type 'AgencyApiController'. Make sure that the controller has a parameterless public constructor.
    </ExceptionMessage>
    <ExceptionType>System.InvalidOperationException</ExceptionType>
    <StackTrace>at System.Web.Http.Dispatcher.DefaultHttpControllerActivator.Create(HttpRequestMessage request, HttpControllerDescriptor controllerDescriptor, Type controllerType) at System.Web.Http.Controllers.HttpControllerDescriptor.CreateController(HttpRequestMessage request) at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__1.MoveNext()
    </StackTrace>
    <InnerException>
        <Message>An error has occurred.</Message>
        <ExceptionMessage>None of the constructors found with 'Autofac.Core.Activators.Reflection.DefaultConstructorFinder' on type 'SSEMPA.DataAccess.Infrastructure.UnitOfWork' can be invoked with the available services and parameters: Cannot resolve parameter 'SSEMPA.DataAccess.Infrastructure.IUserNameProvider userNameProvider' of constructor 'Void .ctor(SSEMPA.DataAccess.Infrastructure.IUserNameProvider , System.String)'.
        </ExceptionMessage>
        <ExceptionType>Autofac.Core.DependencyResolutionException</ExceptionType>

我尝试过为 IUserNameProvider 和连接字符串使用命名参数，但这并没有改变任何东西。看起来这应该可行，所以我一定是遗漏了一些小东西。

感谢您看到这里。

Answer 1

除了控制台应用程序之外，您还需要为 WebAPI 执行额外的配置和设置。查看此处的文档以获取说明:Autofac Web Api Integration