The Pentair Legend filter bag has the U shaped snap-lock closure. When you disconnected the bag from the vacuum tube, you should push this U lock, swing it away, and open the bag. Done! Now you can throw the debris, wash the bag, swing the U shaped lock closure back, and reinstall the filter for next cleaning.
Also, a wet bag is heavier than a dry one. So, if you dry the bag with the debris before emptying, the process will come faster, easier, and more hygienic.