Login using Facebook, missing namespace?

I am trying to integrate a login with facebook feature in my websit开发者_如何学编程e and following this article.

This line gives me a "Missing directive or assembly reference error. The type or namespace could not be found." I have placed the binaries as well.

API api = new API();

Which namespace contains the API class or is it no longer supported?

Facebook API class doesn't exist anymore

If you're using Visual Studio, press Ctrl + . while your caret is within API to see what namespaces contain the API class.