I'm finishing my basement and adding a wet bar. I want the sink in the corner on a 45 deg. Angle. Do I need to buy the corner cabinet before running the plumbing so I know axactly where to stub out the drain and supply lines?

Not necessarily, if you are using standard 24" deep kitchen cabinets, the dimensions of the back of the cabinet will be 36" in each direction. This is necessary in order to have enough room in the front of the cabinet for a reasonable door. The height of the stub out will be the usual. The interior of most corner cabinets are pretty much open so you have lots of room to work. If you are going to use a deep sink you might want to plumb the drain a couple of inches low to accommodate that. All that being said it won't hurt to check the dimensions of the cabinet and the sink, even if you don't purchase now. You might also want to think about desired shelf height so that you don't have to cut up the shelf too much for the plumbing.

Thanks so much Harold. That's kind of what I figured but wanted to check for sure. Didn't want to have to rip out my 1 1/2" pvc.