Twitter OAuth Echo for windows APPs | PIN Code issue

I created an WPF app which uses Twitter OAuth Echo for windows app

do we need to get the pin code every time we need access from windows app to twitter?

or do we need to get it once and store it on a place to use it every time?

here is the example I have followed;

http://blogs.southworks.net/开发者_JAVA百科jpgarcia/2010/07/31/using-twitpic-api-20-oauth-echo-from-a-c-client-to-upload-pictures/

Thanks.

The PIN is entered into your application by the user, and your application passes it back to Twitter in exchange for a pair of tokens. You store the tokens in a settings file or database or something and use them for future Twitter API requests.