I usually cycle in street clothes, often in a skirt or dress. (“Can I ride in this?” has become a major criterion when I shop for new duds.) Depending on wind speed and direction, this entails some risk of exposing more leg than I’d like. It’s a pain to keep tugging at a hem while I’m pedaling.
A friend just shared this brilliant, simple solution.
Unfolded NYC 
Very amusing! And maybe practical, providing your skirt doesn’t wrinkle madly in that one spot, or if it shakes out easily.
I’ve been known to wear dark boy short styles underneath skirts, which look less like dainties-flashing and more like sports-shorts-showing in case of skirt-flip. Though they admittedly don’t do much for the bareness factor.
This reminds me of a trick (not specifically relevant to biking) for cowl-necked blouses and shirts with a draped front: I always hand-sew a dime at the center front. The very slight weight keeps the collar where it’s meant to be.
Apparently this video has gotten over 2 million hits since Cyclehack posted it! Seems to me one could do something similar with a pair of strong magnets, with less wrinkling.
The dime trick is pretty brilliant too.