Twitter Integration with OAuth

Twitter Integration with OAuth

I have been trying to establishing an integration with twitter, what i
need is just below features.
I should be able to extract all the tweets for my account and display it
in my application.
I should be able to post status when i enter a text in my textbox and
click on submit.
I have tried multiple ways, even used 3rd party Libraries like
TweetSharp(it worked pretty well.) As i need to deliver this to a client,
i dont want to use any third party tools, as there will be no one to
support in case of any issues.
First think it should be completely free. So i have tried using OAuth as
explained in the below link. i have updated the twitter api version to 1.1
and added my Consumer Key, Secret, AccessToken and Secret. I executed the
application. To my surprise, my message was posted on to the twitter. but
when i changed the status and executed again, it stopped working and it
keep gives my un authorized error.
The example i m following might not be the complete one, may be i need to
regenerate a access key and do something else. I m confused. can you
please help me how i can proceed further and with link to any post with
complete code.
http://www.codeproject.com/Articles/247336/Twitter-OAuth-authentication-using-Net
Thank you.