I need to qualify my response first, I have only been there for corporate events so obviously everyone was either in a suit or dress pants and a dress shirt, ladies were skirts or some kind of dress.

I have seen them turn people away who haven't been dressed appropriately but those were more teenagers with ripped pants and the like. The only thing is that if you were to go there in a pair of jeans, they might not throw you out but you will feel out of place.

Its definitely upscale though, I'd say just dress formally.