Are you allowed to being a camera inside without getting stopped by security? Like a DSLR

I didnt have an issue I think it depends on the artist you are going to see.

It depends on the band/artist, e.g. Grateful Dead has always allowed professional recording equipment.

How so? I'm going to see an artist in November. I recently saw an artist in Montclair NJ and they said I couldn't bring it in. That's why I'm asking So I wouldn't repeat the same problem

Yep it will be a problem!!