Blazor WebAssembly uses the AuthorizationMessageHandler exception

[wgh2019]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

I am following these instructions from the documentation for attaching authentication tokens to outgoing HTTP requests:
like the documentation

https://learn.microsoft.com/en-us/aspnet/core/blazor/security/webassembly/additional-scenarios?view=aspnetcore-8.0#handle-token-request-errors

Using a AuthorizationMessageHandler as described does not work at all; the request doesn't even send to the API.

Either something is broken or the documentation is unclear.

Can't the AuthorizationMessageHandler be used directly?

My code

        public static async Task Main(string[] args)
        {
            var builder = WebAssemblyHostBuilder.CreateDefault(args);
            builder.RootComponents.Add<App>("#app");
            builder.RootComponents.Add<HeadOutlet>("head::after");
            builder.Services.AddApiAuthorization();
            builder.Services.AddScoped<IAccessTokenProvider, CustomerAccessTokenProvider>();
            builder.Services.AddScoped<AuthorizationMessageHandler>();
            builder.Services.AddScoped(sp => new HttpClient(sp.GetRequiredService<AuthorizationMessageHandler>().ConfigureHandler(
                authorizedUrls: new[] { builder.HostEnvironment.BaseAddress }
                ))
            { BaseAddress = new Uri(builder.HostEnvironment.BaseAddress) });

            await builder.Build().RunAsync();
        }

Expected Behavior

Authorization: Bearer token should be attached to outgoing request

Steps To Reproduce

No response

Exceptions (if any)

crit: Microsoft.AspNetCore.Components.WebAssembly.Rendering.WebAssemblyRenderer[100]
      Unhandled exception rendering component: The inner handler has not been assigned.
System.InvalidOperationException: The inner handler has not been assigned.
   at System.Net.Http.DelegatingHandler.SetOperationStarted()
   at System.Net.Http.DelegatingHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
   at Microsoft.AspNetCore.Components.WebAssembly.Authentication.AuthorizationMessageHandler.<>n__0(HttpRequestMessage request, CancellationToken cancellationToken)
   at Microsoft.AspNetCore.Components.WebAssembly.Authentication.AuthorizationMessageHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
   at System.Net.Http.HttpClient.<SendAsync>g__Core|83_0(HttpRequestMessage request, HttpCompletionOption completionOption, CancellationTokenSource cts, Boolean disposeCts, CancellationTokenSource pendingRequestsCts, CancellationToken originalCancellationToken)
   at System.Net.Http.Json.HttpClientJsonExtensions.<<FromJsonAsyncCore>g__Core|12_0>d`2[[BlazorApp2.Pages.Weather.WeatherForecast[], BlazorApp2, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[System.Text.Json.JsonSerializerOptions, System.Text.Json, Version=8.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51]].MoveNext()
   at BlazorApp2.Pages.Weather.OnInitializedAsync() in E:\Users\wgh\source\repos\BlazorApp2\BlazorApp2\Pages\Weather.razor:line 44
   at Microsoft.AspNetCore.Components.ComponentBase.RunInitAndSetParametersAsync()

.NET Version

net 8.0

Anything else?

No response

[MackinnonBuck]

Thanks for reaching out, @wgh2019.

Per the docs, you'll need to call AddHttpMessageHandler().

Could you please try doing this and letting us know if that solves the issue? Thanks.

[dotnet-policy-service]

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