Autofac.Core.Registration.ComponentNotRegisteredException：请求的服务“ApplicationDbContext”尚未注册

Question

我在启动应用程序时收到错误：

尝试连接数据库时发生错误。(Myproj.Web.Program) Autofac.Core.Registration.ComponentNotRegisteredException：请求的服务“Myproj.Infrastruct.Data.ApplicationDbContext”尚未注册。要避免此异常，请注册一个组件来提供服务，使用 IsRegistered() 检查服务注册，或者使用 ResolveOptional() 方法来解析可选依赖项。 在 Autofac.ResolutionExtensions.ResolveService（IComponentContext 上下文、Service 服务、IEnumerable

1 parameters) at Autofac.ResolutionExtensions.Resolve(IComponentContext context, Type serviceType, IEnumerable

1 个参数） 在 Autofac.ResolutionExtensions.Resolve（IComponentContext 上下文，类型 serviceType） 在 Autofac.Extensions.DependencyInjection.AutofacServiceProvider.GetRequiredService（类型 serviceType） 在 Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService（IServiceProvider 提供程序，类型 serviceType） 在 Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService[T]（IServiceProvider 提供程序） 在 C:\proj\myproj\src\Myproj.Web\Program.cs 中的 Myproj.Web.Program.Main(String[] args)：第 45 行

这是我的Program.cs

public class Program
{
    public static bool DatabaseUnavailable = false;
    public static void Main(string[] args)
    {
        CultureInfo.DefaultThreadCurrentCulture = new CultureInfo("en-US");

        var config = new ConfigurationBuilder().AddJsonFile("appsettings.json").Build();
        Log.Logger = new LoggerConfiguration().ReadFrom.Configuration(config).CreateLogger();

        try
        {
            Log.Information("MyProg Application Starting Up");

            var host = CreateHostBuilder(args).Build();

            using (var scope = host.Services.CreateScope())
            {
                var services = scope.ServiceProvider;

                try
                {
                    var context = services.GetRequiredService<ApplicationDbContext>(); // ERROR

似乎当应用程序尝试从 IoC 容器（本例中为 Autofac）解析

ApplicationDbContext

时，它找不到它。这可能是因为它没有正确注册，或者注册被覆盖或丢失。

这是代码：

1. Program.cs：这是错误的根源，特别是在：

var context = services.GetRequiredService<ApplicationDbContext>();

程序尝试从 DI 容器获取

ApplicationDbContext

的实例，但由于未注册而失败。

2. StartupSetup.cs：这是将

   ApplicationDbContext

   添加到

   IServiceCollection

   的位置。

public static class StartupSetup
{
    public static void AddDbContext(this IServiceCollection services, string connectionString) =>
        services.AddDbContext<ApplicationDbContext>(options =>
        {
            options.UseSqlServer(connectionString,
                providerOptions =>
                {
                    providerOptions
                        .EnableRetryOnFailure(
                            maxRetryCount: 5, 
                            maxRetryDelay: TimeSpan.FromSeconds(30),
                            errorNumbersToAdd: null)
                        .UseQuerySplittingBehavior(QuerySplittingBehavior.SplitQuery);
                });
            options.EnableSensitiveDataLogging();

    // ... rest of the code

3. Startup.cs：这是配置服务的地方，检查

   AddDbContext

   是否正确调用至关重要。我打过电话：

string connectionString = Configuration.GetConnectionString("MyWebApp");
services.AddDbContext(connectionString);

这应该将

ApplicationDbContext

添加到

IServiceCollection

。但是，这并不能保证它已在 Autofac 中注册。

4. Program.cs 和 Startup.cs：我使用 Autofac 作为 DI 容器，并且有一些特定配置将 Autofac 与 ASP.NET Core 集成：

.UseServiceProviderFactory(new AutofacServiceProviderFactory())

和

Startup.cs

：

public void ConfigureContainer(ContainerBuilder builder)
{
    builder.RegisterModule(new DefaultInfrastructureModule(_env.EnvironmentName == "Development",
        Assembly.GetExecutingAssembly()));
    // ... rest of the code
}

如何确保

ApplicationDbContext

也在 Autofac 的

ContainerBuilder

中正确注册？

Autofac 模块定义如下：

public class DefaultInfrastructureModule : Module
    {
        private readonly bool _isDevelopment = false;
        private readonly List<Assembly> _assemblies = new List<Assembly>();

        public DefaultInfrastructureModule(bool isDevelopment, Assembly callingAssembly = null)
        {
            _isDevelopment = isDevelopment;
            var coreAssembly = Assembly.GetAssembly(typeof(IUserResolverService));
            var infrastructureAssembly = Assembly.GetAssembly(typeof(Repository));
            _assemblies.Add(coreAssembly);
            _assemblies.Add(infrastructureAssembly);
            if (callingAssembly != null)
            {
                _assemblies.Add(callingAssembly);
            }
        }

        protected override void Load(ContainerBuilder builder)
        {
            if (_isDevelopment)
            {
                RegisterDevelopmentOnlyDependencies(builder);
            }
            else
            {
                RegisterProductionOnlyDependencies(builder);
            }
            RegisterCommonDependencies(builder);
        }

        private void RegisterCommonDependencies(ContainerBuilder builder)
        {
            //var infrastructureAssembly = Assembly.GetAssembly(typeof(EfRepository));
            builder
                .RegisterAssemblyTypes(_assemblies.ToArray())
                .PublicOnly()
                .Where(t =>
                t.Name.EndsWith("Repository") ||
                t.Name.EndsWith("Factory") ||
                t.Name.EndsWith("Service") ||
                t.Name.EndsWith("Generator") ||
                false
                )
                .AsImplementedInterfaces()
                .InstancePerLifetimeScope();
            //builder.RegisterType<EfRepository>().As<IRepository>()
            //    .InstancePerLifetimeScope();

            builder
                .RegisterType<HttpContextAccessor>()
                .As<IHttpContextAccessor>()
                .SingleInstance();

            builder
                .RegisterType<Mediator>()
                .As<IMediator>()
                .InstancePerLifetimeScope();

            builder.Register<ServiceFactory>(context =>
            {
                var c = context.Resolve<IComponentContext>();
                return t => c.Resolve(t);
            });

            var mediatrOpenTypes = new[]
            {
                typeof(IRequestHandler<,>),
                typeof(IRequestExceptionHandler<,,>),
                typeof(IRequestExceptionAction<,>),
                typeof(INotificationHandler<>),
            };

            foreach (var mediatrOpenType in mediatrOpenTypes)
            {
                builder
                .RegisterAssemblyTypes(_assemblies.ToArray())
                .AsClosedTypesOf(mediatrOpenType)
                .AsImplementedInterfaces();
            }

            builder.RegisterType<EmailSender>().As<IEmailSender>()
                .InstancePerLifetimeScope();
        }

        private void RegisterDevelopmentOnlyDependencies(ContainerBuilder builder)
        {
            // TODO: Add development only services
        }

        private void RegisterProductionOnlyDependencies(ContainerBuilder builder)
        {
            // TODO: Add production only services
        }

    }

Answer 1

最终还是手动注册了DbContext

public void ConfigureContainer(ContainerBuilder builder)
{
    builder.RegisterModule(new DefaultInfrastructureModule(_env.EnvironmentName == "Development",
        Assembly.GetExecutingAssembly()));

    // added this
    builder.RegisterType<ApplicationDbContext>().InstancePerLifetimeScope();

错误消失了