使用 Autofac 注入服务实例

Question

我在 Autofac 注入或注册方面遇到问题。这是我的代码

存储库

 namespace ClientConfiguration.Data.Repository
 {
     public class MappingBaseRepository : RepositoryBase<MappingBase>, IMappingBaseRepository
     {
         public MappingBaseRepository(IDatabaseFactory databaseFactory)
                 : base(databaseFactory)
         {
         }

     }

     public interface IMappingBaseRepository : IRepository<MappingBase>
     {  
     }
 }

服务

namespace ClientConfiguration.Service {

 public interface IMappingBaseService
 {
     IEnumerable<MappingBase> GetElements(); 
     void SaveElement();
 }

 public class MappingBaseService : IMappingBaseService
 {
     private readonly IMappingBaseRepository MappingBaseRepository;
     private readonly IUnitOfWork unitOfWork;


     public MappingBaseService(IMappingBaseRepository MappingBaseRepository, IUnitOfWork unitOfWork)
     {
         this.MappingBaseRepository = MappingBaseRepository;
         this.unitOfWork = unitOfWork;
     }

     #region Members

     public IEnumerable<MappingBase> GetElements()
     {
         var Elements = MappingBaseRepository.GetAll();
         return Elements;
     }

     public void SaveElement()
     {
         unitOfWork.Commit();
     }

     #endregion
 } }

Autofac 初始化

private static void SetAutofacContainer()  {
            var builder = new ContainerBuilder();
            builder.RegisterControllers(Assembly.GetExecutingAssembly());
            builder.RegisterType<UnitOfWork>().As<IUnitOfWork>().InstancePerRequest();
            builder.RegisterType<DatabaseFactory>().As<IDatabaseFactory>().InstancePerRequest();


            // Repositories
            builder.RegisterAssemblyTypes(typeof(ClientElementRepository).Assembly)
                .Where(t => t.Name.EndsWith("Repository"))
                .AsImplementedInterfaces().InstancePerRequest();

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


            IContainer container = builder.Build();
            DependencyResolver.SetResolver(new AutofacDependencyResolver(container));
        }

现在，如果我在控制器内，我就有一个服务对象的实例，没有问题。但是我必须访问我的服务 IMappingBaseService 才能从这个 class 中的数据库获取数据：

namespace ClientConfiguration.Mappings {
    public class CustomDisplayNameAttribute : DisplayNameAttribute {

        private static IMappingBaseService mappingBaseService { get; set; }

        public CustomDisplayNameAttribute(string value)
            : base(GetMessageFromResource(value)) {
        }

        private static string GetMessageFromResource(string value) {

            var els = mappingBaseService.GetElements().ToList();
            //get value from DB
            //mappingBaseService is always null
            return "";
        }
    }
}

如有任何帮助，我们将不胜感激！提前致谢。

Answer 1

代码演示如：

namespace ClientConfiguration.Mappings {
    public class CustomDisplayNameAttribute : DisplayNameAttribute {

        private static IMappingBaseService _mappingBaseService { get; set; }

        public CustomDisplayNameAttribute(string value, IMappingBaseService mappingBaseService)
            : base(GetMessageFromResource(value, mappingBaseService)) {
        }

        private static string GetMessageFromResource(string value, IMappingBaseService mappingBaseService) {
            _mappingBaseService  = mappingBaseService;
            var els = _mappingBaseService .GetElements().ToList();
            //OR var els = mappingBaseService.GetElements().ToList();
            //get value from DB
            //mappingBaseService is always null
            return "";
        }
    }
}

Answer 2

问题是我从 DisplayNameAttribute (ASP.NET MVC) 中附加了 CustomDisplayName

 public class ClientElementsViewModel {
        private static IMappingBaseService _mappingBaseService;
        public ClientElementsViewModel(IMappingBaseService mappingBaseService) {
            _mappingBaseService = mappingBaseService;
        }
        [Key]
        [Display(Name = "Id")]
        public long ClientElementId { get; set; }
        [CustomDisplayName("", _mappingBaseService)]
        public string CompanyCode { get; set; }
        //[CustomDisplayName("")]
        public string WebAppBaseUrl { get; set; }
        //[CustomDisplayName("")]
        public string GuestTraveller { get; set; }
    }

我有这个错误

Error 3 An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type D:\CDS_ADMIN\ClientConfiguration.Web\ViewModel\ClientElementsViewModel.cs 22 32 ClientConfiguration.Web

Answer 3

也许你可以修复代码注册autofac，因为autofac只注册接口，例如：

    builder.RegisterAssemblyTypes(typeof(IClientElementRepository).Assembly)
                .Where(t => t.Name.EndsWith("Repository"))
                .AsImplementedInterfaces().InstancePerRequest();
    // Services
            builder.RegisterAssemblyTypes(typeof(IClientElementService).Assembly)
               .Where(t => t.Name.EndsWith("Service"))
               .AsImplementedInterfaces().InstancePerRequest();

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

Answer 4

解决方案是使用属性注入（在 autofac init 中实例化 class）

我们必须添加这一行

builder.Register(c => new CustomDisplayNameAttribute {
_mappingBaseService = c.Resolve<IMappingBaseService>() });

并在 CustomDisplayNameAttribute 中添加空构造函数

public CustomDisplayNameAttribute() {}

和

public IMappingBaseService _mappingBaseService { get; set; }

为了获取我们使用的对象

var _mappingBaseService = DependencyResolver.Current.GetService<IMappingBaseService>();

使用 Autofac 注入服务实例

Injecting an instance of a service with Autofac

c#

asp.net-mvc

ioc-container

autofac

.net-4.5