Google Data Authentication in C# with 2-Step Verification

use an application password https://www.google.com/settings/security

I understand that in concept, but need help in hammering out the details.  If you were going to modify the class I posted, where exactly would you start?

Please note: I have already created a new "Client ID for native application" at the Google Developers Console.  See the attachment.
Screenshot-2014-09-20-08.07.59.png

It appears to me that modifying the old class is not feasible.  So, I am writing a new one using the new V3 interface.

I'm getting a type conversion error and I don't understand why.  Please look at the comment that starts with Error 1 and advise.

using System;
using System.IO;
using System.Collections.Generic;
using System.Collections;
using System.Linq;
using System.Text;
using System.Diagnostics;

//For use in class CalandarMain
//using Google.GData.Client;
//using Google.GData.Extensions;
//using Google.GData.Calendar;


//For use in class CalandarMainV3  :  An entirly new class needed to 
using System.Threading;
using System.Threading.Tasks;
using Google;
using Google.Apis.Auth.OAuth2;
using Google.Apis.Calendar.v3;
using Google.Apis.Calendar.v3.Data;
using Google.Apis.Services;
using Google.Apis.Util.Store;

    public class CalandarMainV3
    {
        const String ClientSecretsFile = "C:\\Users\\User1\\Documents\\Visual Studio 2010\\Projects\\Programming\\Projects\\Google Ops\\client_secrets.json";

        const String CalAppName = "MyCalAppV3";

        bool m_Init;

        public CalandarMainV3()
        {
            m_Init = AuthGoogleDataInterface();
        }

        private bool AuthGoogleDataInterface()
        {
            bool b_success;
            try
            {
                UserCredential credential;

                using (var stream = new FileStream(ClientSecretsFile, FileMode.Open, FileAccess.Read))
            {
                //Error	1	Cannot implicitly convert type 'System.Threading.Tasks.Task<Google.Apis.Auth.OAuth2.UserCredential>' to 'Google.Apis.Auth.OAuth2.UserCredential'	C:\Users\user1\Documents\Visual Studio 2010\Projects\Programming\Projects\Google Ops\RepBusGoogleCalandar\RepBusGoogleCalandar\ClalandarMain.cs	273	30	RepBusGoogleCalandar
                credential = GoogleWebAuthorizationBroker.AuthorizeAsync(
                    GoogleClientSecrets.Load(stream).Secrets,
                    new[] { Google.Apis.Calendar.v3.CalendarService.Scope.Calendar },
                    "user",
                    CancellationToken.None,
                    new FileDataStore("Calendar.MyCal")
                    );
            }
                Console.WriteLine("AuthGoogleDataInterface: Success");
                b_success = true;
            }
            catch (Exception e)
            {
                string cs_err;
                cs_err = e.Message;
                Console.WriteLine(cs_err);
                Console.WriteLine(e.Source);
                Console.WriteLine("AuthGoogleDataInterface: Fail");
                b_success = false;
                throw;
            }

            return b_success;
        }
    }
}

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The code below complies correctly and runs, but I am now having a problem with the CLIENT SECRETS file.

using System;
using System.IO;
using System.Collections.Generic;
using System.Collections;
using System.Linq;
using System.Text;
using System.Diagnostics;

//For use in class CalandarMainV3  :  An entirely new class needed to 
using System.Threading;
using System.Threading.Tasks;
using Google;
using Google.Apis.Auth.OAuth2;
using Google.Apis.Calendar.v3;
using Google.Apis.Calendar.v3.Data;
using Google.Apis.Services;
using Google.Apis.Util.Store;

namespace RepBusGoogleCalendarV3
{
    public class CalandarMainV3
    {
        const String ClientSecretsFile = "C:\\Users\\user1\\Documents\\Visual Studio 2010\\Projects\\Programming\\Projects\\Google Ops\\client_secrets.json";

        bool m_Init;

        public CalandarMainV3()
        {
            Console.WriteLine("Calling: AuthGoogleDataInterface()");
            m_Init = AuthGoogleDataInterface();
        }

        private bool AuthGoogleDataInterface()
        {
            bool b_success;
            try
            {
                Console.WriteLine("New User Credential");
                // New User Credential
                UserCredential credential;
                using (var stream = new FileStream(ClientSecretsFile, FileMode.Open, FileAccess.Read))
                {
                    credential = GoogleWebAuthorizationBroker.AuthorizeAsync(
                        GoogleClientSecrets.Load(stream).Secrets,
                        new[] { CalendarService.Scope.Calendar },
                        "user", CancellationToken.None,
                        null).Result;
                        //new FileDataStore("My.cal")).Result;
                }

                Console.WriteLine("New Service");
                // Create the service.
                var service = new CalendarService(new BaseClientService.Initializer
                {
                    HttpClientInitializer = credential,
                    ApplicationName = "My Calendar API",
                });
                
                Console.WriteLine("AuthGoogleDataInterface: Success");
                b_success = true;
            }
            catch (Exception e)
            {
                string cs_err;
                cs_err = e.Message;
                Console.WriteLine(cs_err);
                Console.WriteLine(e.Source);
                Console.WriteLine("AuthGoogleDataInterface: Fail");
                b_success = false;
                throw;
            }
            return b_success;
        }
    }
}

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Contents of the client_secrets.json file.

{"installed":{"auth_uri":"https://accounts.google.com/o/oauth2/auth","client_secret":"xxxxxxxxxxxxxxxxxxxxxxxx","token_uri":"https://accounts.google.com/o/oauth2/token","client_email":"","redirect_uris":["urn:ietf:wg:oauth:2.0:xxx","xxx"],"client_x509_cert_url":"","client_id":"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.apps.googleusercontent.com","auth_provider_x509_cert_url":"https://www.googleapis.com/oauth2/v1/certs"}}

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When I run the program, it loads a web page with the following contents:

401. That’s an error.

Error: invalid_client

no application name

Request Details
scope=https://www.googleapis.com/auth/calendar
response_type=code
redirect_uri=http://localhost:00000/authorize/
access_type=offline
client_id=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.apps.googleusercontent.com

That’s all we know.

What am I doing wrong?

That fact that a project name hadn't been set up yet was key.  That should be documented better.