I have developed a couple of form based windows application in vb.net for a client and they all work well and he paid me through a freelance site. I have handed over the executable and the setup to the client and all was well. Now the client wants the source code for the application. Is there a general practice on sharing the source code with the client?

Please note - the client never mentioned he needs the source code and he is now asking for it after a week after the app was completed and he made the payment.

I don't mind sharing the source code, but I am not sure if I should. This probably means the client would not hire me again and the bigger question is the source code really his property?

This question may have been asked a few times, but I cannot still draw a conclusion on what is right.

update

To answer some of the questions:

1. The source code was not mentioned at all. There was no exclusive contract signed except for the usual agreement of the freelance site.
2. I am not sure if software development comes under work for hire and is it valid for users outside of the US?
3. The reason for not sharing the source code was this was a very small project and I got paid for a mere few hours. So if I have an option then definitely I would want to keep the source code to myself as that gives a possibility of the client coming back. The application works flawlessly and the code is solid. Also, the task that the client wanted to achieve was very challenging and I would not like other programmers (competitors) to know how I achieved it.

So unless I get the confirmation that the source code is purely the property of the client, I would not be willing to share it.