They definitely work I've used one but then you can get other problems as a result, it might put them off hunting for example or cause nervousness if you get it wrong.
I would try and find a really good trainer to show you how to use it and also condition the dog to the collar. At first they don't have a clue why they're getting the shock and their first reaction is to run away.
I would consider the e-collar as a last resort which needs to be used with care.
Cheers
Nick