The structure 不…白不…
"If not..., then..."
The colloquial expression 不…白不… 
emphasizes the benefit of doing an action.
emphasizes the benefit of doing an action. Pay attention
白 in this case means "in vain".
This structure is used to make the following sentences:
不拿白不拿 .
Literally, it can be translated as "you can't miss the chance to take it" or "it would be foolish not to take it".
A verb is placed after 不.
.
Literally, it can be translated as "you can't miss the chance to take it" or "it would be foolish not to take it".
A verb is placed after 不.Scheme
不
verb
白不
verb
Pay attention
This structure is only used in colloquial speech.
Examples
今天是他请客，不吃白不吃
Today is his treat — it would be foolish to refuse free food
jīntiān shì tā qǐngkè, bù chī bái bù chī
那么重要的活动，不去白不去
It's such an important event, you can't not go
nàme zhòngyào de huódòng, bú qù bái bú qù
不要白不要，哪怕要了又白要
It would be foolish to refuse it, even if it's pointless to agree with it
bú yào bái bú yào, nǎpà yào le yòu bái yào