While it's a fun thought, using a traditional hairnet on your beard would likely be uncomfortable and ineffective. Beards are thick and tend to move, so a hairnet wouldn't stay in place well.
However, there are some alternatives:
* Beard covers are becoming increasingly popular. These are usually made of a lightweight, breathable fabric that can be pulled over your beard to keep it contained.
* Beard wraps are similar to beard covers, but they are usually made of a more elastic material and are worn around the neck.
* Beard snoods are a type of beard wrap that is typically worn for warmth.
If you are looking to keep your beard clean and out of the way, you might consider using a beard brush or beard comb to style it. You could also try using beard oil or beard balm to help keep it soft and manageable.