Async validation lands in Minimal APIs with .NET 11 Preview 6
Preview 6 adds AsyncValidationAttribute and IAsyncValidatableObject so DataAnnotations rules can hit the database before your endpoint runs, without blocking a thread.
Tag: aspnetcore
53 posts · Page 1 of 6
How to add a health check endpoint to a minimal API in ASP.NET Core 11
A complete, working guide to health checks in an ASP.NET Core 11 minimal API: AddHealthChecks and MapHealthChecks, custom IHealthCheck classes returning Healthy/Degraded/Unhealthy, the AddDbContextCheck EF Core probe, tag-based liveness and readiness endpoints for Kubernetes, a JSON ResponseWriter, ResultStatusCodes, securing the endpoint with RequireAuthorization and RequireHost, and pushing results with IHealthCheckPublisher.
How to add an endpoint filter to a minimal API in ASP.NET Core 11
A complete, working guide to endpoint filters in an ASP.NET Core 11 minimal API: AddEndpointFilter with an inline delegate, IEndpointFilter classes with DI, GetArgument and the Arguments list, short-circuiting with Results.Problem, FIFO/FILO ordering across multiple filters, group-level filters on MapGroup, and AddEndpointFilterFactory for signature-aware filters.
ASP.NET Core 11 Preview 6 turns on automatic CSRF protection
Preview 6 rejects unsafe cross-origin browser requests by default, reading the Sec-Fetch-Site header instead of an antiforgery token. Here is what it blocks and how to opt out.
Fix: "413 Request Entity Too Large" when uploading a file to an ASP.NET Core endpoint
Kestrel caps request bodies at 30,000,000 bytes by default and returns 413 when you exceed it. Raise MaxRequestBodySize globally, per endpoint, or in web.config behind IIS.
Fix: System.InvalidOperationException: Headers are read-only, response has already started
You set a header, status code, or content type after the body was already flushed. Set all headers before the first write, or guard with HttpResponse.HasStarted and OnStarting.
How to add response compression to an ASP.NET Core 11 API
A complete guide to response compression in ASP.NET Core 11: AddResponseCompression and UseResponseCompression, the new built-in Zstandard provider alongside Brotli and Gzip, compression levels, EnableForHttps and the CRIME/BREACH risk, custom MIME types, middleware ordering, and when to let the reverse proxy do it instead.
How to return a typed Results<T1, T2> union from a minimal API endpoint in ASP.NET Core 11
Declare the handler's return type as Results<Ok<T>, NotFound> and return TypedResults.Ok / TypedResults.NotFound: the union gives compile-time checking that the handler only returns what it declares, and it self-describes to OpenAPI so you never write .Produces by hand. Covers async handlers, the six-type limit, and testing in ASP.NET Core 11.
How to add output caching to a minimal API in ASP.NET Core 11
A complete, working guide to output caching in an ASP.NET Core 11 minimal API: AddOutputCache and UseOutputCache, CacheOutput on endpoints and MapGroup, named and base policies, Expire, VaryByQuery and VaryByHeader, tag-based eviction with EvictByTagAsync, cache stampede protection, ETag revalidation, and a Redis backing store.
How to customize the OpenAPI document with AddOperationTransformer and AddSchemaTransformer in ASP.NET Core 11
A deep dive into the built-in OpenAPI transformer pipeline in .NET 11: operation vs schema transformers, the context objects, execution order, DI-activated transformers, and recipes for headers, responses, examples, and per-property tweaks.