从多个 HttpClient 类型注入单个 HttpClient 接口类型

Question

我有以下课程：

public class RestRepository<TDbRecord> : IRepository<TDbRecord> where TDbRecord : class
    {
        #region Fields
        private readonly HttpClient _httpClient;
        #endregion

        #region ctor
        public RestRepository(HttpClient httpClient)
        {
            _httpClient = httpClient;
        }
        #endregion
        ...
    }

该接口有多个需要通过 HTTP 请求执行的操作（Get、GetSpecific Post、Post List...）。

在启动服务中，我正在配置一些具有不同基地址的'HttpClient`，如下所示：

services.AddHttpClient<IRepository<TDbRecordClassA>>(client => client.BaseAddress = new Uri(baseAddress, "api/ClassA"));
services.AddHttpClient<IRepository<TDbRecordClassB>>(client => client.BaseAddress = new Uri(baseAddress, "api/ClassB"));
services.AddHttpClient<IRepository<TDbRecordClassC>>(client => client.BaseAddress = new Uri(baseAddress, "api/ClassC"));
services.AddHttpClient<IRepository<TDbRecordClassD>>(client => client.BaseAddress = new Uri(baseAddress, "api/ClassD"));

以前，我会将它们定义为单例，在启动时构造类，然后将它们注入其他类：

public ClassDActionsHandler(<IRepository<TDbRecordClassD>)… 

然而，现在，当我尝试注入类时，使用 AddHttpClient() 而不在启动期间构造类会给我以下异常：

应用程序启动异常 System.Exception：无法为“x.Startup”类型的“Configure”方法的参数“ClassDActionsHandler”解析“x.y.IClassDActionsHandler”类型的服务。 ---> System.InvalidOperationException：适用于类型 'x.DAL.IRepository1[x.y.z.x.y.z.TDbRecordClassD]' could not be located. Ensure the type is concrete and services are registered for all parameters of a public constructor. at Microsoft.Extensions.DependencyInjection.ActivatorUtilities.FindApplicableConstructor(Type instanceType, Type[] argumentTypes, ConstructorInfo& matchingConstructor, Nullable1[]& parameterMap) 的构造函数 在 Microsoft.Extensions.DependencyInjection.ActivatorUtilities.CreateFactory（类型 instanceType，Type[] argumentTypes） 在 Microsoft.Extensions.Http.DefaultTypedHttpClientFactory1.Cache.<>c.<.cctor>b__7_0() at System.Threading.LazyInitializer.EnsureInitializedCore[T](T& target, Boolean& initialized, Object& syncLock, Func1 valueFactory) 在 Microsoft.Extensions.Http.DefaultTypedHttpClientFactory1.Cache.get_Activator() at Microsoft.Extensions.Http.DefaultTypedHttpClientFactory1.CreateClient(HttpClient httpClient) 在 Microsoft.Extensions.DependencyInjection.HttpClientBuilderExtensions.c__DisplayClass9_01.<AddTypedClient>b__0(IServiceProvider s) at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitFactory(FactoryCallSite factoryCallSite, ServiceProviderEngineScope scope) at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor2.VisitCallSite(IServiceCallSite callSite, TArgument 参数) 在 Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitTransient（TransientCallSite transientCallSite，ServiceProviderEngineScope 范围） 在 Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor2.VisitCallSite(IServiceCallSite callSite, TArgument argument) at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, ServiceProviderEngineScope scope) at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor2.VisitCallSite(IServiceCallSite callSite, TArgument 参数) 在 Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped（ScopedCallSite scopedCallSite，ServiceProviderEngineScope 范围） 在 Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitSingleton（SingletonCallSite singletonCallSite，ServiceProviderEngineScope 范围） 在 Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor2.VisitCallSite(IServiceCallSite callSite, TArgument argument) at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, ServiceProviderEngineScope scope) at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor2.VisitCallSite(IServiceCallSite callSite, TArgument 参数) 在 Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped（ScopedCallSite scopedCallSite，ServiceProviderEngineScope 范围） 在 Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitSingleton（SingletonCallSite singletonCallSite，ServiceProviderEngineScope 范围） 在 Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(IServiceCallSite callSite, TArgument 参数) 在 Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.Resolve（IServiceCallSite callSite，ServiceProviderEngineScope 范围） 在 Microsoft.Extensions.DependencyInjection.ServiceLookup.DynamicServiceProviderEngine.c__DisplayClass1_0.b__0（ServiceProviderEngineScope 范围） 在 Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngine.GetService（类型 serviceType，ServiceProviderEngineScope serviceProviderEngineScope） 在 Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService（类型 serviceType） 在 Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService（IServiceProvider 提供程序，类型 serviceType） 在 Microsoft.AspNetCore.Hosting.Internal.ConfigureBuilder.Invoke（对象实例，IApplicationBuilder 构建器） --- 内部异常堆栈跟踪结束 --- 在 Microsoft.AspNetCore.Hosting.Internal.ConfigureBuilder.Invoke（对象实例，IApplicationBuilder 构建器） 在 Microsoft.AspNetCore.Hosting.Internal.ConfigureBuilder.c__DisplayClass4_0.b__0（IApplicationBuilder 生成器） 在 Microsoft.AspNetCore.Hosting.ConventionBasedStartup.Configure（IApplicationBuilder 应用程序） 在 Microsoft.AspNetCore.Mvc.Internal.MiddlewareFilterBuilderStartupFilter.c__DisplayClass0_0.g__MiddlewareFilterBuilder|0（IApplicationBuilder 构建器） 在 Microsoft.AspNetCore.HostFilteringStartupFilter.c__DisplayClass0_0.b__0（IApplicationBuilder 应用程序） 在 Microsoft.AspNetCore.Hosting.Internal.AutoRequestServicesStartupFilter.c__DisplayClass0_0.b__0（IApplicationBuilder 生成器） 在 Microsoft.AspNetCore.Hosting.Internal.WebHost.BuildApplication()

Answer 1

我认为您需要将您的服务注册码更改为以下内容：

services.AddHttpClient<IRepository<TDbRecordClassA>, RestRepository<TDbRecordClassA>> (client => client.BaseAddress = new Uri(baseAddress, "api/ClassA"));
services.AddHttpClient<IRepository<TDbRecordClassB>, RestRepository<TDbRecordClassB>> (client => client.BaseAddress = new Uri(baseAddress, "api/ClassB"));
services.AddHttpClient<IRepository<TDbRecordClassC>, RestRepository<TDbRecordClassC>> (client => client.BaseAddress = new Uri(baseAddress, "api/ClassC"));
services.AddHttpClient<IRepository<TDbRecordClassD>, RestRepository<TDbRecordClassD>> (client => client.BaseAddress = new Uri(baseAddress, "api/ClassD"));