Hi Liz,
Usually, I wear a pair of my black Nike workout shorts underneath a dress if it is a dark color. They are fitted enough and short enough not to show under the dress. For a light colored dress or skirt, I have a pair of white workout shorts that I got from Carushka a number of years ago. There are also ball "panties and shorts" called Fancy Pants specifically made for wear under a skirt or dress that do not have skorts. I have a pair of them although I don't like them as well as my workout shorts.
Joyce