How to check offline for Facebook permissions

Question

Hey all,

I have Facebook Toolkit for .NET and I am trying to check whether my application has permissions for a user.

I have the userId of the user, and I am trying to do:

_facebookAPI.Session.RequiredPermissions = listExtended;
                _facebookAPI.Session.SessionKey = Resources.FbApplicationKey;
                _facebookAPI.Session.SessionSecret = Resources.FbSecretKey;                
                _facebookAPI.Session.Login();                 

                if (_facebookAPI.Users.HasAppPermission(Enums.ExtendedPermissions.publish_stream) &&
                    _facebookAPI.Users.HasAppPermission(Enums.ExtendedPermissions.offline_access))

I get session is invalid error.

How can I check permissions in offline mode?

thank you