AddHttpMessageHandler not using correct scope in Blazor Wasm app

[mrpmorris]

Describe the bug

When using Microsoft.Extensions.Http AddHttpClient and AddHttpMessageHandler, the instance of T belongs to a different ServiceProvider than the ServiceProvider used to generate a Blazor page - even though T is registered as scoped.

To Reproduce

Create a new Blazor WASM project

Add NuGet reference Microsoft.Extensions.Http

Create a class as follows

	public class MyDelegatingHandler : DelegatingHandler
	{
		private readonly IServiceProvider ServiceProvider;

		public MyDelegatingHandler(IServiceProvider serviceProvider)
		{
			ServiceProvider = serviceProvider;
		}

		protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
		{
			Console.WriteLine("Http service provider hash = " + ServiceProvider.GetHashCode());
			return base.SendAsync(request, cancellationToken);
		}
	}

In Program.cs remove the registration of HttpClient and replace it with the following

			builder.Services.AddScoped<MyDelegatingHandler>();
			builder.Services
					.AddHttpClient("local", c => c.BaseAddress = new Uri(builder.HostEnvironment.BaseAddress))
					.AddHttpMessageHandler<MyDelegatingHandler>();

Edit FetchData.razor
Remove the injection of HttpClient and relace it with

@inject IHttpClientFactory HttpClientFactory
@inject IServiceProvider ServiceProvider

Replace OnInitializedAsync with the following code

protected override async Task OnInitializedAsync()
{
	var httpClient = HttpClientFactory.CreateClient("local");
	Console.WriteLine("Page service provider hash = " + ServiceProvider.GetHashCode());
	forecasts = await httpClient.GetFromJsonAsync<WeatherForecast[]>("sample-data/weather.json");
}

Now run the app, open the console window in the browser, and navigate to the Fetch Data page.

Expected

The hash code for the page and the http delegate should be the same.

Actual

They are different, therefore they are both running within separate IServiceProvider containers.

[javiercn]

@mrpmorris thanks for contacting us.

HttpClientFactory controls the lifetime of the clients and the handlers. The recommendation is to register the handlers as transient.

[mrpmorris]

HI @javiercn - Is HttpClientFactory registered as Singleton or Scoped?

[javiercn]

@mrpmorris IHttpClientFactory is a singleton I believe, but it is best to check the sources.

[mrpmorris]

@javiercn I'm afraid your suggestion isn't a suitable solution. It seems that a Transient service will resolve dependencies as Transient too, and so not receive a reference to the service scoped to the current user.

I'll report it in another repository, thanks.