Is it common courtesy to bring something such as food to a dinner party or bbq?
It would depend on what kind of dinner party it was. If I am throwing a dinner party, I normally do not want my guests to bring anything, I will provide all the food. If I am attending a dinner party, I will ask the host/hostess if I can bring anything. If it is family or a close friend, I will just bring something without asking. My best advice would be to call the host/hostess and ask if there is anything you can bring. Or you can bring flowers or another small gift as a “thank you” to the hostess for inviting you over.