HTTP endpoints

A controller action that does nothing but deserialize a request, call Send, and translate a Result into a status code is boilerplate. Mediant.AspNetCore removes it.

dotnet add package Mediant.AspNetCore

Annotate the command

[HttpEndpoint("POST", "/api/orders", Tags = ["Orders"], SuccessStatusCode = 201)]
[Transactional]
[Auditable]
public record CreateOrder(string UserId, List<OrderItem> Items) : ICommand<Result<Guid>>;

Map them

app.MapMediantEndpoints(typeof(Program).Assembly);

The assembly is scanned for [HttpEndpoint], and each annotated request becomes a minimal-API route that binds the body (or route/query values), dispatches through the full behavior pipeline, and maps the Result to HTTP.

Attribute options

Property	Purpose
Method	"GET", "POST", … (constructor argument)
Route	The route template (constructor argument)
SuccessStatusCode	200 by default; set 201 for creates
Group	Route group to nest under
Tags	OpenAPI tags
Summary / Description	OpenAPI metadata

Result maps to status

The ErrorType on the failure decides the response. Nothing to wire up.

Result	Response
Success	200 OK (or 201 Created, if configured)
Validation	400 — RFC 7807 ValidationProblemDetails, one entry per field
Unauthorized	401
Forbidden	403
NotFound	404
Conflict	409
Failure	422 Unprocessable Entity
Unavailable	503
Internal / anything else	500

Note

A domain rule rejecting a request is a 422, not a 500. Your alerting should not fire because a customer tried to cancel an already-shipped order.

All failures are returned as ProblemDetails, so a client gets a consistent, machine-readable body.

Queries with route parameters

[HttpEndpoint("GET", "/api/orders/{id}", Tags = ["Orders"])]
[Cacheable(durationSeconds: 60, CacheKeyPrefix = "orders:")]
public record GetOrderById(Guid Id) : IQuery<Result<Order>>;

{id} binds to the Id property. A cache hit skips the handler entirely, but still passes through logging and auditing.

Keep your controllers

None of this is exclusive. MapMediantEndpoints maps only the annotated types — everything else stays in your controllers, and you can call mediator.Send(...) from them as usual.

public class OrdersController(IMediator mediator) : ControllerBase
{
    [HttpPost]
    public async Task<IActionResult> Create(CreateOrder cmd)
    {
        var result = await mediator.Send(cmd);
        return result.Match(id => Created($"/api/orders/{id}", id), this.Problem);
    }
}