How Google API V 3.0 .Net library and Google OAuth2 Handling refresh token

Question

In my application I am using Google API V 3.0 .Net library with Google OAuth2 to synchronize Google calender and outlook calender. I am using below code to get the Google.Ap

Answer 1

For me, client library did not do the refreshing, not even creating the refresh token.
I check whether the token is expired and refresh. (Token has a 1hour life time). credential.Token.IsExpired will tell you whether it is expired, credential.Token.RefreshToken(userid) will refresh the necessary token.

Answer 2

Spent the last two days figuring this out myself. The library does not refresh the tokens automatically unless you specify "access_type=offline".

https://developers.google.com/api-client-library/dotnet/guide/aaa_oauth

I'm gonna paste the code I'm using and if there is anything you don't understand, just ask. I have read so many posts and I litteraly got this working right now so there is some commented code and it has not been refactored yet. I hope this will help someone. The NuGet packages I'm using are these:

Google.Apis.Auth.MVC

Google.Apis.Calendar.v3

Code:

AuthCallbackController:

[AuthorizationCodeActionFilter]
public class AuthCallbackController : Google.Apis.Auth.OAuth2.Mvc.Controllers.AuthCallbackController
{
protected static readonly ILogger Logger = ApplicationContext.Logger.ForType<AuthCallbackController>();

/// <summary>Gets the authorization code flow.</summary>
protected IAuthorizationCodeFlow Flow { get { return FlowData.Flow; } }

/// <summary>
/// Gets the user identifier. Potential logic is to use session variables to retrieve that information.
/// </summary>
protected string UserId { get { return FlowData.GetUserId(this); } }

/// <summary>
/// The authorization callback which receives an authorization code which contains an error or a code.
/// If a code is available the method exchange the coed with an access token and redirect back to the original
/// page which initialized the auth process (using the state parameter).
/// <para>
/// The current timeout is set to 10 seconds. You can change the default behavior by setting 
/// <see cref="System.Web.Mvc.AsyncTimeoutAttribute"/> with a different value on your controller.
/// </para>
/// </summary>
/// <param name="authorizationCode">Authorization code response which contains the code or an error.</param>
/// <param name="taskCancellationToken">Cancellation token to cancel operation.</param>
/// <returns>
/// Redirect action to the state parameter or <see cref="OnTokenError"/> in case of an error.
/// </returns>
[AsyncTimeout(60000)]
public async override Task<ActionResult> IndexAsync(AuthorizationCodeResponseUrl authorizationCode,
   CancellationToken taskCancellationToken)
{
    if (string.IsNullOrEmpty(authorizationCode.Code))
    {
        var errorResponse = new TokenErrorResponse(authorizationCode);
        Logger.Info("Received an error. The response is: {0}", errorResponse);
        Debug.WriteLine("Received an error. The response is: {0}", errorResponse);
        return OnTokenError(errorResponse);
    }

    Logger.Debug("Received \"{0}\" code", authorizationCode.Code);
    Debug.WriteLine("Received \"{0}\" code", authorizationCode.Code);


    var returnUrl = Request.Url.ToString();
    returnUrl = returnUrl.Substring(0, returnUrl.IndexOf("?"));

    var token = await Flow.ExchangeCodeForTokenAsync(UserId, authorizationCode.Code, returnUrl,
        taskCancellationToken).ConfigureAwait(false);

    // Extract the right state.
    var oauthState = await AuthWebUtility.ExtracRedirectFromState(Flow.DataStore, UserId,
        authorizationCode.State).ConfigureAwait(false);

    return new RedirectResult(oauthState);
}

protected override Google.Apis.Auth.OAuth2.Mvc.FlowMetadata FlowData
{
    get { return new AppFlowMetadata(); }
}

protected override ActionResult OnTokenError(TokenErrorResponse errorResponse)
{
    throw new TokenResponseException(errorResponse);
}


//public class AuthCallbackController : Google.Apis.Auth.OAuth2.Mvc.Controllers.AuthCallbackController
//{
//    protected override Google.Apis.Auth.OAuth2.Mvc.FlowMetadata FlowData
//    {
//        get { return new AppFlowMetadata(); }
//    }
//}

}

Method for Controller calling Google API

    public async Task<ActionResult> GoogleCalendarAsync(CancellationToken cancellationToken)
    {
        var result = await new AuthorizationCodeMvcApp(this, new AppFlowMetadata()).
            AuthorizeAsync(cancellationToken);

        if (result.Credential != null)
        {
            //var ttt = await result.Credential.RevokeTokenAsync(cancellationToken);

            //bool x = await result.Credential.RefreshTokenAsync(cancellationToken);

            var service = new CalendarService(new BaseClientService.Initializer()
            {
                HttpClientInitializer = result.Credential,
                ApplicationName = "GoogleApplication",
            });
            var t = service.Calendars;

            var tt = service.CalendarList.List();

            // Define parameters of request.
            EventsResource.ListRequest request = service.Events.List("primary");
            request.TimeMin = DateTime.Now;
            request.ShowDeleted = false;
            request.SingleEvents = true;
            request.MaxResults = 10;
            request.OrderBy = EventsResource.ListRequest.OrderByEnum.StartTime;

            // List events.
            Events events = request.Execute();
            Debug.WriteLine("Upcoming events:");
            if (events.Items != null && events.Items.Count > 0)
            {
                foreach (var eventItem in events.Items)
                {
                    string when = eventItem.Start.DateTime.ToString();
                    if (String.IsNullOrEmpty(when))
                    {
                        when = eventItem.Start.Date;
                    }
                    Debug.WriteLine("{0} ({1})", eventItem.Summary, when);
                }
            }
            else
            {
                Debug.WriteLine("No upcoming events found.");
            }


            //Event myEvent = new Event
            //{
            //    Summary = "Appointment",
            //    Location = "Somewhere",
            //    Start = new EventDateTime()
            //        {
            //            DateTime = new DateTime(2014, 6, 2, 10, 0, 0),
            //            TimeZone = "America/Los_Angeles"
            //        },
            //    End = new EventDateTime()
            //        {
            //            DateTime = new DateTime(2014, 6, 2, 10, 30, 0),
            //            TimeZone = "America/Los_Angeles"
            //        },
            //    Recurrence = new String[] {
            //        "RRULE:FREQ=WEEKLY;BYDAY=MO"
            //        },
            //    Attendees = new List<EventAttendee>()
            //        {
            //        new EventAttendee() { Email = "johndoe@gmail.com" }
            //        }
            //};

            //Event recurringEvent = service.Events.Insert(myEvent, "primary").Execute();

            return View();
        }
        else
        {
            return new RedirectResult(result.RedirectUri);
        }
    }

Derived class of FlowMetadata

public class AppFlowMetadata : FlowMetadata
    {
        //static readonly string server = ConfigurationManager.AppSettings["DatabaseServer"];
        //static readonly string serverUser = ConfigurationManager.AppSettings["DatabaseUser"];
        //static readonly string serverPassword = ConfigurationManager.AppSettings["DatabaseUserPassword"];
        //static readonly string serverDatabase = ConfigurationManager.AppSettings["DatabaseName"];
    ////new FileDataStore("Daimto.GoogleCalendar.Auth.Store")
    ////new FileDataStore("Drive.Api.Auth.Store")
    //static DatabaseDataStore databaseDataStore = new DatabaseDataStore(server, serverUser, serverPassword, serverDatabase);


    private static readonly IAuthorizationCodeFlow flow =
new ForceOfflineGoogleAuthorizationCodeFlow(new GoogleAuthorizationCodeFlow.Initializer
{
    ClientSecrets = new ClientSecrets
    {
        ClientId = "yourClientId",
        ClientSecret = "yourClientSecret"

    },
    Scopes = new[]
    {
CalendarService.Scope.Calendar, // Manage your calendars
//CalendarService.Scope.CalendarReadonly // View your Calendars
    },
    DataStore = new EFDataStore(),
});

    public override string GetUserId(Controller controller)
    {
        // In this sample we use the session to store the user identifiers.
        // That's not the best practice, because you should have a logic to identify
        // a user. You might want to use "OpenID Connect".
        // You can read more about the protocol in the following link:
        // https://developers.google.com/accounts/docs/OAuth2Login.

        //var user = controller.Session["user"];
        //if (user == null)
        //{
        //    user = Guid.NewGuid();
        //    controller.Session["user"] = user;
        //}
        //return user.ToString();

        //var store = new UserStore<ApplicationUser>(new ApplicationDbContext());
        //var manager = new UserManager<ApplicationUser>(store);
        //var currentUser = manager.FindById(controller.User.Identity.GetUserId());

        return controller.User.Identity.GetUserId();

    }

    public override IAuthorizationCodeFlow Flow
    {
        get { return flow; }
    }

    public override string AuthCallback
    {
        get { return @"/GoogleApplication/AuthCallback/IndexAsync"; }
    }
}

Entity framework 6 DataStore class

 public class EFDataStore : IDataStore
    {
        public async Task ClearAsync()
        {
            using (var context = new ApplicationDbContext())
            {
                var objectContext = ((IObjectContextAdapter)context).ObjectContext;
                await objectContext.ExecuteStoreCommandAsync("TRUNCATE TABLE [Items]");
            }
        }

        public async Task DeleteAsync<T>(string key)
        {
            if (string.IsNullOrEmpty(key))
            {
                throw new ArgumentException("Key MUST have a value");
            }

        using (var context = new ApplicationDbContext())
        {
            var generatedKey = GenerateStoredKey(key, typeof(T));
            var item = context.GoogleAuthItems.FirstOrDefault(x => x.Key == generatedKey);
            if (item != null)
            {
                context.GoogleAuthItems.Remove(item);
                await context.SaveChangesAsync();
            }
        }
    }

    public Task<T> GetAsync<T>(string key)
    {
        if (string.IsNullOrEmpty(key))
        {
            throw new ArgumentException("Key MUST have a value");
        }

        using (var context = new ApplicationDbContext())
        {
            var generatedKey = GenerateStoredKey(key, typeof(T));
            var item = context.GoogleAuthItems.FirstOrDefault(x => x.Key == generatedKey);
            T value = item == null ? default(T) : JsonConvert.DeserializeObject<T>(item.Value);
            return Task.FromResult<T>(value);
        }
    }

    public async Task StoreAsync<T>(string key, T value)
    {
        if (string.IsNullOrEmpty(key))
        {
            throw new ArgumentException("Key MUST have a value");
        }

        using (var context = new ApplicationDbContext())
        {
            var generatedKey = GenerateStoredKey(key, typeof(T));
            string json = JsonConvert.SerializeObject(value);

            var item = await context.GoogleAuthItems.SingleOrDefaultAsync(x => x.Key == generatedKey);

            if (item == null)
            {
                context.GoogleAuthItems.Add(new GoogleAuthItem { Key = generatedKey, Value = json });
            }
            else
            {
                item.Value = json;
            }

            await context.SaveChangesAsync();
        }
    }

    private static string GenerateStoredKey(string key, Type t)
    {
        return string.Format("{0}-{1}", t.FullName, key);
    }
}

Derived class for GoogleAuthorizationCodeFlow. Enabling long-lived refresh token that take care of automatically "refreshing" the token, which simply means getting a new access token.

https://developers.google.com/api-client-library/dotnet/guide/aaa_oauth

internal class ForceOfflineGoogleAuthorizationCodeFlow : GoogleAuthorizationCodeFlow
{
    public ForceOfflineGoogleAuthorizationCodeFlow(GoogleAuthorizationCodeFlow.Initializer initializer) : base (initializer) { }

    public override AuthorizationCodeRequestUrl CreateAuthorizationCodeRequest(string redirectUri)
    {
        return new GoogleAuthorizationCodeRequestUrl(new Uri(AuthorizationServerUrl))
        {
            ClientId = ClientSecrets.ClientId,
            Scope = string.Join(" ", Scopes),
            RedirectUri = redirectUri,
            AccessType = "offline",
            ApprovalPrompt = "force"
        };
    }
}

GoogleAuthItem is used with EFDataStore

public class GoogleAuthItem
{
    [Key]
    [MaxLength(100)]
    public string Key { get; set; }

    [MaxLength(500)]
    public string Value { get; set; }
}

public DbSet<GoogleAuthItem> GoogleAuthItems { get; set; }

Answer 3

That's the butty of the client library! this magic is done for you automatically :)

UserCredential implements both IHttpExecuteInterceptor and IHttpUnsuccessfulResponseHandler. so whenever the access token is going to be expired, or is already expired, the client makes a call to the authorization server to refresh the token and get a new access token (which is valid for the next 60 minutes).

Read more about it at https://developers.google.com/api-client-library/dotnet/guide/aaa_oauth#credentials