Missing assembely reference error after adding Facebook.dll using c# asp.net -

i working on login facebook in app using c# asp.net.i added facebook.dll inside reference section still showing following error.

error:

the type of namespace name facebookapi not exist in namespace facebook. 

errors coming below line of code.

facebook.facebookapi api = new facebook.facebookapi(getaccesstoken()); 

please let me know version mismatch or ? please me.

to honest don't see facebookapi class in sdk reference. maybe looking other class:

facebookclient client = new facebook.facebookclient(getaccesstoken()); 

are sure referring latest sdk documentation?