using Google.Contacts;
using Google.GData.Client;
using Google.GData.Contacts;
using Google.GData.Extensions;

using Google.Contacts;
using Google.GData.Client;
using Google.GData.Contacts;
using Google.GData.Extensions;
using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Text;
using System.Web;
using System.Web.Mvc;

namespace GoogleContactImport.Controllers
{
    public class HomeController : Controller
    {
        public ActionResult Index()
        {
            return View();
        }

        public ActionResult Import()
        {
            string clientId = "";  // here you need to add your google client id
            string redirectUrl = "http://localhost:1713/Home/AddGoogleContacts"; // here your redirect action method NOTE: you need to configure same url in google console
            Response.Redirect("https://accounts.google.com/o/oauth2/auth?redirect_uri=" + redirectUrl + "&amp&response_type=code&amp&client_id=" + clientId + "&amp&scope=https://www.google.com/m8/feeds/&approval_prompt=force&access_type=offline");
            return View();
        }

        public ActionResult AddGoogleContacts()
        {
            string code = Request.QueryString["code"];
            if (!string.IsNullOrEmpty(code))
            {
                var contacts = GetAccessToken().ToArray();
                if (contacts.Length > 0)
                {
                  // You will get all contacts here
                    return View("Index",contacts);
                }
                else
                {
                    return RedirectToAction("Index","Home");
                }
            }
            else
            {
                return RedirectToAction("Index", "Home");
            }
        }
        public List<GmailContacts> GetAccessToken()
        {
            string code = Request.QueryString["code"];
            string google_client_id = ""; //your google client Id
            string google_client_sceret = ""; // your google secret key
            string google_redirect_url = "http://localhost:1713/MyContact/AddGoogleContacts";


            HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create("https://accounts.google.com/o/oauth2/token");
            webRequest.Method = "POST";
            string parameters = "code=" + code + "&client_id=" + google_client_id + "&client_secret=" + google_client_sceret + "&redirect_uri=" + google_redirect_url + "&grant_type=authorization_code";
            byte[] byteArray = Encoding.UTF8.GetBytes(parameters);
            webRequest.ContentType = "application/x-www-form-urlencoded";
            webRequest.ContentLength = byteArray.Length;
            Stream postStream = webRequest.GetRequestStream();
            // Add the post data to the web request
            postStream.Write(byteArray, 0, byteArray.Length);
            postStream.Close();
            WebResponse response = webRequest.GetResponse();
            postStream = response.GetResponseStream();
            StreamReader reader = new StreamReader(postStream);
            string responseFromServer = reader.ReadToEnd();
            GooglePlusAccessToken serStatus = JsonConvert.DeserializeObject<GooglePlusAccessToken>(responseFromServer);
            /*End*/
            return GetContacts(serStatus);
        }

        public List<GmailContacts> GetContacts(GooglePlusAccessToken serStatus)
        {
            string google_client_id = "";  //client id
            string google_client_sceret = ""; //secret key
            /*Get Google Contacts From Access Token and Refresh Token*/
            // string refreshToken = serStatus.refresh_token;
            string accessToken = serStatus.access_token;
            string scopes = "https://www.google.com/m8/feeds/contacts/default/full/";
            OAuth2Parameters oAuthparameters = new OAuth2Parameters()
            {
                ClientId = google_client_id,
                ClientSecret = google_client_sceret,
                RedirectUri = "http://localhost:1713/Home/AddGoogleContacts",
                Scope = scopes,
                AccessToken = accessToken,
                //  RefreshToken = refreshToken
            };

            RequestSettings settings = new RequestSettings("App Name", oAuthparameters);
            ContactsRequest cr = new ContactsRequest(settings);
            ContactsQuery query = new ContactsQuery(ContactsQuery.CreateContactsUri("default"));
            query.NumberToRetrieve = 5000;
            Feed<Contact> ContactList = cr.GetContacts();

            List<GmailContacts> olist = new List<GmailContacts>();
            foreach (Contact contact in ContactList.Entries)
            {
                foreach (EMail email in contact.Emails)
                {
                    GmailContacts gc = new GmailContacts();
                    gc.EmailID = email.Address;
                    var a = contact.Name.FullName;
                    olist.Add(gc);
                }
            }
            return olist;
        }

        public class GmailContacts
        {
            public string EmailID
            {
                get { return _EmailID; }
                set { _EmailID = value; }
            }
            private string _EmailID;
        }

        public class GooglePlusAccessToken
        {

            public GooglePlusAccessToken()
            { }


            public string access_token
            {
                get { return _access_token; }
                set { _access_token = value; }
            }
            private string _access_token;

            public string token_type
            {
                get { return _token_type; }
                set { _token_type = value; }
            }
            private string _token_type;

            public string expires_in
            {
                get { return _expires_in; }
                set { _expires_in = value; }
            }
            private string _expires_in;

        }
    }
}

<a href='@Url.Action("Import", "Home")'>Import Google Contacts</a>