Marking a topic with "de hua"
的话 (de huà) is a particle that can be put at the end of a phrase to express a condition, a little bit like "if". It can be used independently, or with 如果, both meaning "if".
- 如果 你 去 的话,帮 我 问 她 好。
- 下次 有 时间 的话,一定 要 找 我 玩儿。
- 如果 你 不 忙 的话,可以 帮 我 联系 客户 吗?
的话 can also be used to introduce a topic which the speaker wants to go on and comment on:
- 云南 的话,春天 去 最好。
- 晚上的话,当然 方便。
In these example sentences, the action is left out, so 云南的话 more formally could be expressed as 如果去云南的话。