Autofac 异常：无法解析构造函数'Void .ctor 的参数

Question

我有以下错误：

ExceptionMessage=None of the constructors found with 'Autofac.Core.Activators.Reflection.DefaultConstructorFinder' on type 'RestAPI.DevelopersController' can be invoked with the available services and parameters: Cannot resolve parameter 'Services.DevelopersService userService' of constructor 'Void .ctor(Services.DevelopersService)'.

Global.asax.cs

protected void Application_Start()
    {
        GlobalConfiguration.Configure(WebApiConfig.Register);
        AutoMapperConfig.RegisterMappings();
        var builder = new ContainerBuilder();
        builder.RegisterModule(new ServiceModule());
        builder.RegisterModule(new ORMModule());
        builder.RegisterApiControllers(Assembly.GetExecutingAssembly()).PropertiesAutowired();
        var container = builder.Build();
        var resolver = new AutofacWebApiDependencyResolver(container);
        GlobalConfiguration.Configuration.DependencyResolver = resolver;
    }

ServiceModule.cs

public class ServiceModule : Autofac.Module
{
    protected override void Load(ContainerBuilder builder)
    {
        builder.RegisterAssemblyTypes(Assembly.Load("Services"))
                 .Where(t => t.Name.EndsWith("Service"))
                 .AsImplementedInterfaces()
                 .InstancePerLifetimeScope();
    }
}

ORMModule.cs

public class ORMModule : Autofac.Module
{
    protected override void Load(ContainerBuilder builder)
    {
        builder.RegisterType(typeof(DatabaseContext)).As(typeof(DbContext)).InstancePerLifetimeScope();
    }
}

DevelopersController

public class DevelopersController : ApiController
{
    private DevelopersService _developersService;

    public DevelopersController(DevelopersService userService)
    {
        _developersService = userService;
        _developersService.SetIdentity(HttpContext.Current.Request.LogonUserIdentity.Name.ToString().Substring(4));
    }

DevelopersService.cs

public class DevelopersService : IService<User>
{
    private DatabaseContext _db;

    public DevelopersService(DatabaseContext db)
    {
        _db = db;
    }

    public void SetIdentity(string username)
    {

    }

    public User Create(User entity)
    {
        return new User();
    }
    public User Read(User Id)
    {
        return new User();
    }
    public void Update(User user)
    {

    }
    public void Delete(User Id)
    {

    }
    public IEnumerable<User> GetAll()
    {
        return _db.Users.AsEnumerable();
    }
}

IService.cs

public interface IService<T> where T : BaseEntity
{
    void SetIdentity(string identity);
    T Create(T entity);
    T Read(T Id);
    void Update(T entity);
    void Delete(T Id);
    IEnumerable<T> GetAll();
}

我该如何解决？

Answer 1

当 Autofac 尝试实例化 DevelopersController 时会出现此错误消息。为了创建一个新的 DevelopersController，它必须提供一个实例 DevelopersService，但其中 none 个已在 Autofac 中注册。

即使下面这段代码

builder.RegisterAssemblyTypes(Assembly.Load("Services"))
       .Where(t => t.Name.EndsWith("Service"))
       .AsImplementedInterfaces()
       .InstancePerLifetimeScope();

在 Autofac 中注册一个 DevelopersService，它不会将其注册为 DevelopersService，而是注册为已实现的接口（即 IService<User>）

为了解决您的问题，您可以更改注册以将服务注册为自身

builder.RegisterAssemblyTypes(Assembly.Load("Services"))
       .Where(t => t.Name.EndsWith("Service"))
       .AsImplementedInterfaces()
       .AsSelf()
       .InstancePerLifetimeScope();

或将您的 DevelopersController 更改为不依赖 DevelopersService 而依赖 IService<USer>

public class DevelopersController : ApiController
{
    private IService<USer> _userService;

    public DevelopersController(IService<USer> userService)
    {
        _userService= userService;
        _userService.SetIdentity(HttpContext.Current.Request.LogonUserIdentity.Name.ToString().Substring(4));
    }

我会推荐这个解决方案。

Answer 2

希望我的回答仍然有帮助，我认为问题是缺乏对可能位于其他项目的 DevelopersService class 的引用。试试下面的代码。

        builder.RegisterAssemblyTypes(typeof(DevelopersService).Assembly)
            .Where(t => t.Name.EndsWith("Service"))
            .AsImplementedInterfaces().InstancePerRequest();

Answer 3

好的，所以我正在使用 nopcommerce，在我的依赖注册器中我有一个类型

已输入：

builder.RegisterType<CustomerReturnsService>().As<CustomerReturnsService>();

应该是

builder.RegisterType<CustomerReturnsService>().As<ICustomerReturnsService>();

注意上次客户 returns 服务中的 I。它链接到服务的界面。

Autofac 异常：无法解析构造函数'Void .ctor 的参数

Autofac Exception: Cannot resolve parameter of constructor 'Void .ctor

c#

asp.net

asp.net-web-api

autofac