Heller was about DC's ban on the ownership of a handgun. It overturned the ban...but did not overhaul all of DC's gun laws. It's now possible to get a permit to purchase a firearm as a DC resident. It does nothing, however, to address the laws prohibiting carry or possession by anyone else.
While I'm not an expert on DC law, I would imagine the laws on carrying a concealed knife are no friendlier than the laws on carrying a firearm. In general DC, like so many other crime-ridden cesspools, has decided that honest people shouldn't be able to defend themselves. Thus if you don't have to be in DC, I'd avoid it like the plague.How bad are the knife laws of those places?