dependency-injection - 使用 IHttpFactory 注入(inject)服务时，构造函数无法位于 Blazor 服务器中

Question

我正在尝试在 startup.cs 中注册一个使用 IHttpClientFactory 的服务。当我访问注入(inject)此服务的页面时出现异常(它确实启动了)。我尝试使用 HttpContext 而不是工厂，但没有收到以下错误。

错误:

InvalidOperationException: A suitable constructor for type'dida.Data.Member.MemberService' could not be located.Ensure the type is concrete and services are registered for allparameters of a public constructor.

服务:

namespace dida.Data.Member
{
    public class MemberService
    {
        private readonly IHttpClientFactory _clientFactory;

        public MemberService(IHttpClientFactory clientFactory)
        {
            _clientFactory = clientFactory;
        }

        public async Task<IEnumerable<Member>> GetMembers()
        {
            var request  = new HttpRequestMessage(HttpMethod.Get, "users?_token=*");
            var client = _clientFactory.CreateClient("myapp");
            var response = await client.SendAsync(request);

            if (response.IsSuccessStatusCode)
            {
                using var responseStream = await response.Content.ReadAsStreamAsync();
                return await JsonSerializer.DeserializeAsync<IEnumerable<Member>>(responseStream);
            }
            else
            {
                throw new HttpRequestException("No success status code, got the following: " + response.StatusCode);
            }

        }
    }
}

启动:

services.AddHttpClient<MemberService>("myapp", c =>
            {
                c.BaseAddress = new Uri("https://myapp.nl/api");
                c.DefaultRequestHeaders.Add("User-Agent", "blazor-server");
            });

完整日志:

Microsoft.Extensions.DependencyInjection.ActivatorUtilities.FindApplicableConstructor(Type instanceType, Type[] argumentTypes, out ConstructorInfo matchingConstructor, out Nullable<int>[] matchingParameterMap)
Microsoft.Extensions.DependencyInjection.ActivatorUtilities.CreateFactory(Type instanceType, Type[] argumentTypes)
Microsoft.Extensions.Http.DefaultTypedHttpClientFactory<TClient>+Cache+<>c.<.cctor>b__7_0()
System.Threading.LazyInitializer.EnsureInitializedCore<T>(ref T target, ref bool initialized, ref object syncLock, Func<T> valueFactory)
System.Threading.LazyInitializer.EnsureInitialized<T>(ref T target, ref bool initialized, ref object syncLock, Func<T> valueFactory)
Microsoft.Extensions.Http.DefaultTypedHttpClientFactory<TClient>+Cache.get_Activator()
Microsoft.Extensions.Http.DefaultTypedHttpClientFactory<TClient>.CreateClient(HttpClient httpClient)
Microsoft.Extensions.DependencyInjection.HttpClientBuilderExtensions+<>c__DisplayClass10_0<TClient>.<AddTypedClientCore>b__0(IServiceProvider s)
Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitFactory(FactoryCallSite factoryCallSite, RuntimeResolverContext context)
Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor<TArgument, TResult>.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitDisposeCache(ServiceCallSite transientCallSite, RuntimeResolverContext context)
Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor<TArgument, TResult>.VisitCallSite(ServiceCallSite callSite, TArgument argument)
Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.Resolve(ServiceCallSite callSite, ServiceProviderEngineScope scope)
Microsoft.Extensions.DependencyInjection.ServiceLookup.DynamicServiceProviderEngine+<>c__DisplayClass1_0.<RealizeService>b__0(ServiceProviderEngineScope scope)
Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngine.GetService(Type serviceType, ServiceProviderEngineScope serviceProviderEngineScope)
Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService(Type serviceType)
Microsoft.AspNetCore.Components.ComponentFactory+<>c__DisplayClass6_0.<CreateInitializer>g__Initialize|2(IServiceProvider serviceProvider, IComponent component)
Microsoft.AspNetCore.Components.ComponentFactory.PerformPropertyInjection(IServiceProvider serviceProvider, IComponent instance)
Microsoft.AspNetCore.Components.ComponentFactory.InstantiateComponent(IServiceProvider serviceProvider, Type componentType)
Microsoft.AspNetCore.Components.RenderTree.Renderer.InstantiateChildComponentOnFrame(ref RenderTreeFrame frame, int parentComponentId)
Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.InitializeNewComponentFrame(ref DiffContext diffContext, int frameIndex)
Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.InitializeNewSubtree(ref DiffContext diffContext, int frameIndex)
Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.InsertNewFrame(ref DiffContext diffContext, int newFrameIndex)
Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.AppendDiffEntriesForRange(ref DiffContext diffContext, int oldStartIndex, int oldEndIndexExcl, int newStartIndex, int newEndIndexExcl)
Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.ComputeDiff(Renderer renderer, RenderBatchBuilder batchBuilder, int componentId, ArrayRange<RenderTreeFrame> oldTree, ArrayRange<RenderTreeFrame> newTree)
Microsoft.AspNetCore.Components.Rendering.ComponentState.RenderIntoBatch(RenderBatchBuilder batchBuilder, RenderFragment renderFragment)
Microsoft.AspNetCore.Components.RenderTree.Renderer.RenderInExistingBatch(RenderQueueEntry renderQueueEntry)
Microsoft.AspNetCore.Components.RenderTree.Renderer.ProcessRenderQueue()
Microsoft.AspNetCore.Components.Rendering.HtmlRenderer.HandleException(Exception exception)
Microsoft.AspNetCore.Components.RenderTree.Renderer.ProcessRenderQueue()
Microsoft.AspNetCore.Components.RenderTree.Renderer.ProcessPendingRender()
Microsoft.AspNetCore.Components.RenderTree.Renderer.AddToRenderQueue(int componentId, RenderFragment renderFragment)
Microsoft.AspNetCore.Components.ComponentBase.StateHasChanged()
Microsoft.AspNetCore.Components.ComponentBase.CallOnParametersSetAsync()
Microsoft.AspNetCore.Components.ComponentBase.RunInitAndSetParametersAsync()
Microsoft.AspNetCore.Components.Rendering.HtmlRenderer.HandleException(Exception exception)
Microsoft.AspNetCore.Components.RenderTree.Renderer.AddToPendingTasks(Task task)
Microsoft.AspNetCore.Components.Rendering.ComponentState.SetDirectParameters(ParameterView parameters)
Microsoft.AspNetCore.Components.RenderTree.Renderer.RenderRootComponentAsync(int componentId, ParameterView initialParameters)
Microsoft.AspNetCore.Components.Rendering.HtmlRenderer.CreateInitialRenderAsync(Type componentType, ParameterView initialParameters)
Microsoft.AspNetCore.Components.Rendering.HtmlRenderer.RenderComponentAsync(Type componentType, ParameterView initialParameters)
Microsoft.AspNetCore.Components.Rendering.RendererSynchronizationContext+<>c__11<TResult>+<<InvokeAsync>b__11_0>d.MoveNext()
Microsoft.AspNetCore.Mvc.ViewFeatures.StaticComponentRenderer.PrerenderComponentAsync(ParameterView parameters, HttpContext httpContext, Type componentType)
Microsoft.AspNetCore.Mvc.ViewFeatures.ComponentRenderer.PrerenderedServerComponentAsync(HttpContext context, ServerComponentInvocationSequence invocationId, Type type, ParameterView parametersCollection)
Microsoft.AspNetCore.Mvc.ViewFeatures.ComponentRenderer.RenderComponentAsync(ViewContext viewContext, Type componentType, RenderMode renderMode, object parameters)
Microsoft.AspNetCore.Mvc.TagHelpers.ComponentTagHelper.ProcessAsync(TagHelperContext context, TagHelperOutput output)
Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperRunner.<RunAsync>g__Awaited|0_0(Task task, TagHelperExecutionContext executionContext, int i, int count)
dida.Pages.Pages__Host.<ExecuteAsync>b__14_1() in _Host.cshtml
+
        <component type="typeof(App)" render-mode="ServerPrerendered" />
Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperExecutionContext.SetOutputContentAsync()
dida.Pages.Pages__Host.ExecuteAsync() in _Host.cshtml
+
    Layout = null;
Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderPageCoreAsync(IRazorPage page, ViewContext context)
Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderPageAsync(IRazorPage page, ViewContext context, bool invokeViewStarts)
Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderAsync(ViewContext context)
Microsoft.AspNetCore.Mvc.ViewFeatures.ViewExecutor.ExecuteAsync(ViewContext viewContext, string contentType, Nullable<int> statusCode)
Microsoft.AspNetCore.Mvc.ViewFeatures.ViewExecutor.ExecuteAsync(ViewContext viewContext, string contentType, Nullable<int> statusCode)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResultFilterAsync>g__Awaited|29_0<TFilter, TFilterAsync>(ResourceInvoker invoker, Task lastTask, State next, Scope scope, object state, bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResultExecutedContextSealed context)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext<TFilter, TFilterAsync>(ref State next, ref Scope scope, ref object state, ref bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeResultFilters()
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResourceFilter>g__Awaited|24_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, object state, bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(ref State next, ref Scope scope, ref object state, ref bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeFilterPipelineAsync()
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.MigrationsEndPointMiddleware.Invoke(HttpContext context)
Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.DatabaseErrorPageMiddleware.Invoke(HttpContext httpContext)
Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.DatabaseErrorPageMiddleware.Invoke(HttpContext httpContext)
Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

Answer 1

要按照您最初使用 IHttpClientFactory 定义的方式使用您的类，您需要以不同方式注册/配置它。

像这样

//adding named client
services.AddHttpClient("myapp", c => {
    c.BaseAddress = new Uri("https://myapp.nl/api");
    c.DefaultRequestHeaders.Add("User-Agent", "blazor-server");
});

//adding regular service
services.AddScoped<MemberService>();

引用 Make HTTP requests using IHttpClientFactory in ASP.NET Core

但是，自从您像这样注册您的类(class)后，您就混淆了如何使用typed 客户端

services.AddHttpClient<MemberService>("myapp", c => ....

注意

A Typed Client is a class that accepts an HttpClient object (injected through its constructor) and uses it to call some remote HTTP service.

引用 Use IHttpClientFactory to implement resilient HTTP requests

例如

public class MemberService
{
    private readonly HttpClient client;

    public MemberService(HttpClient client) {
        this.client = client;
    }

    public async Task<IEnumerable<Member>> GetMembers() {
        var request  = new HttpRequestMessage(HttpMethod.Get, "users?_token=*");
        var response = await client.SendAsync(request);

        if (response.IsSuccessStatusCode) {
            using var responseStream = await response.Content.ReadAsStreamAsync();
            return await JsonSerializer.DeserializeAsync<IEnumerable<Member>>(responseStream);
        } else {
            throw new HttpRequestException("No success status code, got the following: " + response.StatusCode);
        }
    }
}

因此，因为您将您的类注册为类型化客户端但没有相应的构造函数，所以您得到了所述错误。