-다고 하던데 — I heard that..., They said that..., Recalling what was said

This expression is a combination of -는다고 하다, indicating a citation, and -던데, indicating recollection. It is used when recalling or confirming something you heard somebody else say previously. Thus, the correct form of this expression also depends on the sentence type of what was heard previously. The clause that follows this expression can indicate the speaker’s opinion, question, advice or invitation with respect to the topic under discussion.

Details

For adjectives in the present tense, both -냐고 하던데 and -으냐고 하던데 are acceptable, while for verbs in the present tense, both -냐고 하던데 and -느냐고 하던데 are acceptable.

1. The -고 하- of this expression can be omitted.

내일 추워진다고 하던데 아이들이 감기에 걸릴까 봐 걱정이에요.

친구가 홍대 앞에 가자고 하던데 동희 씨는 가 본 적이 있어요?

2. This expression can also come at the end of a sentence. In this position, while still expressing something that the speaker heard previously, it also indicates either the speaker's disagreement with the other person's opinion or the speaker's expectation of a response from the other person.

가: 수정 씨한테도 같이 연극 보자고 할까요?

A: Shall we invite Sujeong to go to see the play, too?

나: 수정 씨는 요즘 바쁘다고 하던데요.

B: (But) Sujeong said she's been busy these days.

가: 마크 씨가 지금 어디에 있는지 아세요?

A: Do you know where Mark is right now?

나: 아까 헬스클럽에 간다고 하던데요.

B: A little while ago, he said he was going to the health club.

가: 한강에서 불꽃놀이 축제를 한다고 하던데 같이 안 갈래요? 나: 네, 좋아요. 정말 멋지겠네요. 같이 가요.

A: I heard (from someone) that there's a fireworks display at the Han River, so would you like to go together? B: Yes, that sounds nice. It should be awesome. Let’s go.

가: 전자사전을 사려고 하는데 어디에 가면 좋을까요? 나: 친구들이 전자 제품을 싸게 사려면 용산에 가라고 하던데 거기에 가 보세요,

A: I’m planning to buy an electronic dictionary, but do you know where I should go? B: My friends said that if you want to buy electronics at a good price, then go to Yongsan, So you should go there.

가: 요즘 머리가빠져서 걱정이에요. 나: 검은콩이 탈모에 좋다고 하던데 검은콩을 좀 먹어 보세요.

A: I'm worried because i've been losing some hair recently. B: I heard black beans are good for curing hair loss, so why not try eating some black beans?