Event messages need to either implement IEvent or match a custom DefiningEventsAs convention. See the message design documentation for more details.
Handling an event
In order to handle an event, implement the IHandleMessages interface in any handler or saga class, where T is the specific event type.
Publishing an event
Call the Publish method to publish an event.
There are a few common scenarios for publishing events. Events might be published:
- from a handler, when processing another message.
public class CreateUserHandler :
IHandleMessages<CreateUserCommand>
{
public Task Handle(CreateUserCommand message, IMessageHandlerContext context)
{
var userCreatedEvent = new UserCreatedEvent
{
Name = message.Name
};
return context.Publish(userCreatedEvent);
}
}
- from a saga handler, when processing another message.
public class CreateUserSaga :
Saga<CreateUserSaga.SagaData>,
IHandleMessages<CreateUserCommand>
{
public Task Handle(CreateUserCommand message, IMessageHandlerContext context)
{
var userCreatedEvent = new UserCreatedEvent
{
Name = message.Name
};
return context.Publish(userCreatedEvent);
}
- at endpoint startup
// Other config
var endpointInstance = await Endpoint.Start(endpointConfiguration);
await endpointInstance.Publish(new MyEvent());
Composing events
In order to support advanced composition scenarios, events can be defined as interfaces. See the Messages as Interfaces for more details.