为什么我在启动应用程序时遇到同样的错误？ "InvalidOperationException: Unable to resolve service"

Question

错误=>

处理请求时出现未处理的异常。 InvalidOperationException：尝试激活 'BookReadingEventWebApplication.Controllers.HomeController' 时无法解析类型 'Business_Logic_Layer.Home.IHomeBLL' 的服务。 Microsoft.Extensions.DependencyInjection.ActivatorUtilities.GetService(IServiceProvider sp, Type type, Type requiredBy, bool isDefaultParameterRequired)

Startup.cs =>

 public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_3_0);
            services.AddAutoMapper(typeof(Startup));
            services.AddDbContext<ApplicationDbContext>(options =>
            options.UseSqlServer(
                Configuration.GetConnectionString("DefaultConnection")));

            services.AddIdentity<IdentityUser, IdentityRole>()
                .AddEntityFrameworkStores<ApplicationDbContext>();

            services.AddScoped<IAccountRepository, AccountRepository>();

            services.AddControllersWithViews();

        }


  [1]: https://i.stack.imgur.com/39YUb.png


**HomeController** =>

 public class HomeController : Controller
    {
        private readonly ILogger<HomeController> _logger;

        public readonly IHomeBLL _BLL;

        public HomeController( ILogger<HomeController> logger, IHomeBLL BLL)
        {
            _logger = logger;
            _BLL = BLL;
        }


        public IActionResult Index()
        {
            var list = _BLL.GetAllEvents();
            return View(list);
        }


**HomeBLL** =>

public class HomeBLL : IHomeBLL
    {
        private Data_Access_Layer.HomeDAL _DAL;

        public HomeBLL(Data_Access_Layer.HomeDAL DAL)
        {
            _DAL = DAL;
        }

        public List<BookReadingEventModel> GetAllEvents()
        {
            return _DAL.GetAllEvents();
        }
    }

**IHomeBLL** =>

public interface IHomeBLL
    {
        public List<BookReadingEventModel> GetAllEvents();
    }

Answer 1

您需要在 ConfigureServices 中注册 IHomeBLL 服务。

例如：

// or AddSingleton or AddTransient
services.AddScoped<IHomeBLL, HomeBLL>();

但是，由于 HomeBLL 依赖于 (Data_Access_Layer.HomeDAL DAL)，您需要遵循此链。

正在注册 HomeDAL

您没有显示 HomeDAL 需要创建的内容，以下是猜测。

这里有一些选项，其中一个可能适用于您的设置。

如果需要创建HomeDAL 'by hand':

// Create 
HomeDAL homeDAL = ...;
services.AddScoped<IHomeBLL>(provider => new HomeBLL(homeDAL));

请注意，如果 HomeDAL 实现一个接口 IHomeDAL 并且 HomeBLL 依赖于 IHomeDAL 可能会更好。然后，如果 HomeDAL 没有任何依赖项，您可以通过以下方式注册它们：

// or AddSingleton or AddTransient
services.AddScoped<IHomeDAL, HomeDAL>();
services.AddScoped<IHomeBLL, HomeBLL>();

为什么我在启动应用程序时遇到同样的错误？ "InvalidOperationException: Unable to resolve service"

Why I am Getting Same Error While Starting Application ? "InvalidOperationException: Unable to resolve service"

c#

asp.net-mvc

正在注册 HomeDAL