Adding HttpClientFactory causing errors with cancellationTokenSource

Question

I have a problem with the HttpClientFactory, i am trying to inject a CancellationTokenSource from DI to my "SomeClient" that configured to be like a:

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

and i am injecting cancellationTokenSource in Startup.cs in the AddScoped<>().

If i add CancellationTokenSource to SomeClient constructor it will say

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

but if i create something like:

services.AddScoped<ISomeClient, SomeClient>();

and make a new local HttpClient in the constructor, and inject CancellationTokenSource, everything will be fine.

So my question is how to use CancellationTokenSource with HttpClientFactory?

Answer 1

For AddHttpClient, it will register SomeClient as Transient. But you register CancellationTokenSource as Scoped. This is the root caused.

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;
    }

So, you could try register CancellationTokenSource as Transient.

services.AddTransient<CancellationTokenSource>();