While her mom could not attend due to unforeseen circumstances, Jin turned up to the party in a Lolita-style outfit with a white Channel 2.55 handbag filled with her mother's business cards. She later won the Best Dressed Award.

Jin, however, was not impressed with the event.

"I hadn't heard about it before. I thought it was just another costume party, but it turned out people are dressed in rather boring clothes," she said.

Wang Yu, a 45-year-old mother of two teenage boys, on the other hand, enjoyed herself thoroughly. Having traveled by train for seven hours from Zhengzhou, Henan province, Wang was among the 70 or so women who signed up for the party as the members of HerRose Club, an exclusive club for female entrepreneurs.

"This is my second year here. I met so many great women here last year that I didn't hesitate at all when the invitation arrived again this year," said Wang, who runs a spa chain and an etiquette school in Zhengzhou.

"I can easily become 'a frog in the well' with what I am doing in Zhengzhou. Being a part of such an event and getting to know the people here prevents that from happening," she added.

Wang Jing, the host of the local event, revealed that local elements infused into the event usually don't come from the young generation.

"This year, we saw more than one group of middle-aged Shanghai aunties bring their homemade marinated pigs' offals and kaofu, a local dish made from wheat gluten that few young people know how to cook," said Wang, a former event planner and a Shanghai native.

Wo Leliu, a 72-year-old grandmother who attended the event with her son and daughter, brought pickled duck necks, grapes and desserts. The retired pediatrician wore a cutout T-shirt dress with lace embroidery and a cream fascinator with feather details, that her daughter bought for her from online marketplace Taobao.

Like most other guests, Wo was eager to share the moment with her friends on WeChat. Her photos, accompanied by the caption "dining in French style with a dress bought from Provence", received 150 likes.

But to Wo, Le Diner en Blanc is not about being seen in fancy clothes or getting to network with others.

"It's very like chengliang," she quipped, referring to the popular activity of playing cards or chatting with neighbors outdoors during the summer nights in a bid to stay cool.