handlers-and-sagas.md

title	summary	component	reviewed	related
Handlers and Sagas	A brief introduction to handlers and sagas	Core	2025-02-19	nservicebus/handlers nservicebus/sagas samples/saga

There are two standard ways of executing code when a message is processed: handlers and sagas.

Handler instances are instantiated on a per-message basis, executed, and then disposed of. These are sometimes referred to as “stateless handlers”.

Saga instances are also instantiated on a per-message basis, executed, and then disposed of. However they differ from handlers in that, once instantiated, they are passed an instance of a "Data" class. The "Saga Data" is persistent state that is shared between a given saga type based on a key. These are sometimes referred to as “stateful handlers”.

Other concepts that both handlers and sagas share:

• Recoverability (i.e. what happens when message processing fails)
• Executed within the same pipeline
• Detected via assembly scanning