In order to use the transactional session feature with MongoDB persistence, add a reference to the NServiceBus. NuGet package.
Configuration
To enable the transactional session feature:
var persistence = config.UsePersistence<MongoPersistence>();
persistence.EnableTransactionalSession();
Opening a session
To open a MongoDB transactional session:
using var childScope = serviceProvider.CreateScope();
var session = childScope.ServiceProvider.GetService<ITransactionalSession>();
await session.Open();
// use the session
await session.Commit();
Transaction usage
Message and database operations made via the the transactional session are committed together once the session is committed:
await session.Open();
// add messages to the transaction:
await session.Send(new MyMessage());
// access the database:
var mongoSession = session.SynchronizedStorageSession.MongoPersistenceSession();
await session.Commit();
See the MongoDB persistence transactions documentation for further details about using the MongoDB transaction.
In order to guarantee atomic consistency across message and database operations, the outbox must be enabled. Otherwise Commit executes database modifications first and then messages are dispatched with best-effort.