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Corvus.JsonSchema

Async Api Producer

recipe JSON Schema C# async api producer

Demonstrates how to publish messages using a generated AsyncAPI 3.0 producer. The code generator reads the Streetlights spec and emits a strongly-typed TurnOnProducer that handles channel-address construction, payload validation, and authentication — you just build the payload and call PublishTurnOnOffAsync.

What This Demonstrates

Feature Where
Typed payload construction via Source pattern TurnOnOffPayload.Source with ref-struct builder
Channel parameter interpolation streetlightId → zero-allocation UTF-8 address
Payload schema validation ValidationMode.Basic or .Detailed
Authentication provider UserPasswordAuthenticationProvider
In-memory transport for testing InMemoryMessageTransport

Prerequisites

dotnet tool install --global Corvus.Json.Cli

Generating the Code

corvusjson asyncapi-generate streetlights.json \
    --rootNamespace Streetlights.Client \
    --outputPath Generated

This produces:

  • TurnOnProducer — typed producer for the turnOn operation with PublishTurnOnOffAsync
  • ReceiveLightMeasurementConsumer — consumer for the receiveLightMeasurement operation (used in 037)
  • IReceiveLightMeasurementHandler — handler interface for incoming messages
  • Message wrappers (TurnOnTurnOnOffMessage, ReceiveLightMeasurementLightMeasuredMessage)
  • 16 model types in Models/ — TurnOnOffPayload, LightMeasuredPayload, JsonDateTime, etc.

How the Generated Code Helps

Payload Construction (Source Pattern)

The generated TurnOnOffPayload.Source uses a ref-struct builder that avoids allocating intermediate objects:

await producer.PublishTurnOnOffAsync(
    payload: new TurnOnOffPayload.Source((ref TurnOnOffPayload.Builder b) =>
    {
        b.Create(command: "on"u8, sentAt: DateTimeOffset.UtcNow);
    }),
    streetlightId: "lamp-42");

Channel Address Construction

The streetlightId parameter is part of the channel address template smartylighting.streetlights.1.0.action.{streetlightId}.turn.on. The generated code constructs the full address using zero-allocation UTF-8 byte manipulation with pooled buffers.

Validation

Pass a ValidationMode to the producer constructor to control payload validation:

Mode Behaviour
ValidationMode.None No validation (fastest, production hot path)
ValidationMode.Basic Boolean pass/fail schema check
ValidationMode.Detailed Full error diagnostics with JSON Pointer locations

Running

dotnet run -f net10.0

Expected output:

Published turnOnOff to lamp-42
Channel: smartylighting.streetlights.1.0.action.lamp-42.turn.on
Payload: {"command":"on","sentAt":"2026-05-26T...+00:00"}
Published authenticated turnOnOff to lamp-99
Channel with param: smartylighting.streetlights.1.0.action.lamp-99.turn.on