Tag: httpclient

The BCL has no ProblemDetails type, and adding a FrameworkReference to Microsoft.AspNetCore.App makes your client refuse to start on a runtime-only container. Here is the 20-line model that does the job, the DelegatingHandler that turns problem+json into a typed exception, and the content-type myth that most answers still repeat.

Aspire's AddServiceDefaults applies a standard resilience handler to every HttpClient. Calling AddStandardResilienceHandler again stacks a second one instead of replacing it. Here are the three real override paths, the -standard options name nobody documents, and the infinite timeout you inherit if you just remove it.

The inner AuthenticationException tells you the real cause: an untrusted chain, a name mismatch, or a TLS version gap. Trust the cert, fix the host name, or align protocols. Do not blanket-disable validation.

Use the Microsoft.Extensions.Http.Resilience handler for HttpClient calls, since it is Polly with HTTP-aware defaults and telemetry in one line. Reach for Polly's ResiliencePipeline directly only when you protect something that is not an HttpClient.

Never new up HttpClient per request. Use IHttpClientFactory to manage lifetime, and add Refit on top when you want a typed interface instead of hand-written request code. Raw singleton HttpClient is fine only for the simplest cases.

HttpClient throws TaskCanceledException for three different reasons: timeout, caller cancellation, or a connection-level abort. Tell them apart with InnerException and CancellationToken.IsCancellationRequested, then fix the right one.

A complete guide to testing HttpClient in .NET 11: why you should not mock HttpClient directly, how to write a stub HttpMessageHandler, swapping the primary handler with IHttpClientFactory, verifying Polly retries, and the WireMock.Net option.