How can I reuse facebook's DotNetOpenAuth accesstoken?

I have successfully authenticated by using C# DotNetOpenAuth according to this tutorial Easy OAuth Login with ASP.NET.

But I have one question. Everytime I access to the web site, it will display a facebook login page then user must click a login button to continue. The question is how can I reuse the first accesstoken to avoid the login page?

Is it possible? Which code statement should I use?

Thank you very much!