In a double-breasted suit, all buttons should be buttoned. You can also deduct only the top one, but you can't do without it. After you sit down, unbutton your clothes, and after you get up, button them as they are.
Extended data:
Suits are also called "suits" and "dresses". Suit is a kind of "foreign culture". In China, people often call a coat with lapels and lapels, three pockets and a length below the hip line a "suit", which is obviously what China people call clothes from the west.
Men's suit
Before the appearance of modern suits, the suits worn by modern western men to attend business occasions had a long and thick black coat, which was called a dress coat. It was not until the end of 19 that Americans began to wear a light coat that was only waist-long, called gunny bag. This has become the standard daytime dress for informal and non-workplace occasions, and even the simplest man will have a suit like this to wear to church on Sunday. Before World War II, this simple suit would be worn with a vest.
On the other hand, evening dress has also developed into an informal dress. The original tuxedo evolved into a small evening dress. Today, the tuxedo has even replaced the tuxedo as the standard dress for evening occasions, while the tuxedo with a long history is only reserved for the most solemn occasions, such as banquets, concerts and award ceremonies. The formal dress during the day is morning dress. Although modern occasions are generally not too rigid in red tape, according to the etiquette required for attending the occasion, the invitation should indicate the dress code.
References:
Set-Baidu Encyclopedia