基本上任何时候您的工作单元要么对外部更改敏感，要么需要能够回滚每个更改，如果发生错误或其他原因.

Basically any time you have a unit of work that is either sensitive to outside changes or needs the ability to rollback every change, if an error occurs or some other reason.

在这里寻找一些出色的答案及其使用原因.