Each message that is dispatched from an Endpoint has a unique identity. NServiceBus generates and stores this value as a header on the message named
NServiceBus.MessageId. If the selected transport supports message identity, and there is value in using the NServiceBus MessageId, this value can be optionally used as the transport level message identity as well.
Many features take advantage of message identity. For example, the Outbox uses message identity to deduplicate messages and recoverability uses message identity to keep track of how many times the endpoint has tried to process a message.
Message identity can be explicitly specified, overriding the default identity provided by NServiceBus.
Specify message identity using the
var options = new SendOptions(); options.SetMessageId(messageId); await handlerContext.Send(new SomeMessage(), options) .ConfigureAwait(false);