An A-line midi dress for cocktail creates a flattering silhouette because the shape is structured and the proportion is balanced. A-line means fitted at the shoulders and bust then flaring from the waist down. Midi length shows the A-line shape fully. The fabric can be cotton or cotton blend or structured silk. A-line shapes work in solid color or print. The simplicity of the silhouette means the neckline and sleeve details become important. These dresses often work with belts to emphasize the waist. A good A-line midi dress in the right color is a reliable choice for almost any cocktail situation. These A-line midi dresses work because the shape is universally flattering and the proportion is always right.