A new unit of work is automatically started when a command (implementing ICommand) is processed. On the other hand, queries (implementing IQuery<T>) do not start a unit of work as they should not modify the domain data (which means they do not need a unit of work) a this paragraph is irrelevant to their processing. The unit of work wraps the effects of a single business transaction defined by the command. When the command handler finishes, the unit of work is automatically committed, or it is canceled when the command handler fails with an exception. The unit of work commits all of its providers – i.e. most importantly, the repository. Thanks to this, it is not necessary (or desirable) to manually save the repository within the command handler.