添加 HttpClientFactory 导致 cancellationTokenSource 出错

Question

我的 HttpClientFactory 有问题，我正在尝试将来自 DI 的 CancellationTokenSource 注入到我的 "SomeClient" 中，配置如下：

services.AddHttpClient<ISomeClient, SomeClient>(a =>
                a.BaseAddress = new Uri(address))

并且我在 AddScoped<>() 的 Startup.cs 中注入 cancellationTokenSource。

如果我将 CancellationTokenSource 添加到 SomeClient 构造函数，它将显示

Cannot resolve scoped service 'System.Threading.CancellationTokenSource' from root provider.

但是如果我创建类似的东西：

services.AddScoped<ISomeClient, SomeClient>();

并在构造函数中新建一个本地HttpClient，并注入CancellationTokenSource，一切都会好起来的。

所以我的问题是如何将 CancellationTokenSource 与 HttpClientFactory 一起使用？

Answer 1

对于AddHttpClient，它将SomeClient注册为Transient。但是你将 CancellationTokenSource 注册为 Scoped。这是根源造成的。

HttpClientFactoryServiceCollectionExtensions.cs

    public static IHttpClientBuilder AddHttpClient<TClient>(this IServiceCollection services)
        where TClient : class
    {
        if (services == null)
        {
            throw new ArgumentNullException(nameof(services));
        }

        AddHttpClient(services);

        var name = TypeNameHelper.GetTypeDisplayName(typeof(TClient), fullName: false);
        var builder = new DefaultHttpClientBuilder(services, name);
        builder.AddTypedClient<TClient>();
        return builder;
    }

HttpClientBuilderExtensions

        public static IHttpClientBuilder AddTypedClient<TClient>(this IHttpClientBuilder builder)
        where TClient : class
    {
        if (builder == null)
        {
            throw new ArgumentNullException(nameof(builder));
        }

        builder.Services.AddTransient<TClient>(s =>
        {
            var httpClientFactory = s.GetRequiredService<IHttpClientFactory>();
            var httpClient = httpClientFactory.CreateClient(builder.Name);

            var typedClientFactory = s.GetRequiredService<ITypedHttpClientFactory<TClient>>();
            return typedClientFactory.CreateClient(httpClient);
        });

        return builder;
    }

因此，您可以尝试将 CancellationTokenSource 注册为 Transient。

services.AddTransient<CancellationTokenSource>();