Thanks for writing. Wild violets can be very difficult to get rid of. A thick layer of mulch will certainly help, but you'll need to pull all the plants you see before you spread the mulch.
I'm sorry, but other than that, there aren't really any other great suggestions I know of other than allowing the violet to act as a groundcover and crowd out other kinds of weeds. Eventually, it can form a relatively thick covering over the ground that still allows taller perennials to grow up through it.
---Justin, Senior Garden Editor, BHG.com