Google Play Service PlusClient only compiles partly

I try to implement Google + signin using Google Play services PlusClient.

I wonder why I can only compile parts of the PlusClient methodes. Example

plusClient.Disconnect(); !!!!! Works

if (plusClient.IsConnected){} !!!!!! Works

Person p = plusClient.GetCurrentPerson(); !!!!! Does not compile

Error 124 The type or namespace name 'Person' could not be found (are you missing a using directive or an assembly reference?) C:\Users\olefa_000\Documents\ONDO_ANDROID\OndoDot_Android\OndoDot_Android\Activities\GoogleLogin.cs 148 13 OndoDot_Android Error 125 'Android.Gms.Plus.PlusClient' does not contain a definition for 'GetCurrentPerson' and no extension method 'GetCurrentPerson' accepting a first argument of type 'Android.Gms.Plus.PlusClient' could be found (are you missing a using directive or an assembly reference?) C:\Users\olefa_000\Documents\ONDO_ANDROID\OndoDot_Android\OndoDot_Android\Activities\GoogleLogin.cs 148 35 OndoDot_Android

I try catch the UserProfile via PlusClient.

I have also tried to run this sample also with same problem

http://motzcod.es/post/67077106339/google-plus-services-login-and-1-in-xamarin-android

/OFK