Michelle Obama wore a black off-the-shoulder Vera Wang Collection mermaid gown to the state dinner in honor of Chinese President Xi Jinping on Friday night. The first lady’s look — hair gathered in that vintage sultry side sweep popular on red carpets and the form-fitting frock’s silhouette — hearkened back to old Hollywood glamour. It was a very Veronica Lake moment. The custom dress was silk crepe with a V-neckline, delicate tulle sleeves and an organza pleated skirt.