使用 IHttpFactory 注入服务时，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 all parameters 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

要按照最初用 IHttpClientFactory 定义的方式使用 class，您需要 register/configure 以不同的方式使用它。

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，您混淆了如何使用 typed 客户端，因为您是这样注册 class

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

备注

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 class 注册为类型化客户端，但没有相应的构造函数，所以出现了上述错误。

使用 IHttpFactory 注入服务时，构造函数无法位于 Blazor 服务器中

When injecting service with IHttpFactory the constructor could not be located in Blazor server

dependency-injection

dotnet-httpclient

blazor

httpclientfactory

blazor-server-side