How to use the Google Contacts API through Oauth2 authentication

Question

I have this code below to get calendar entries using the Google Calendar API ( https://developers.google.com/google-apps/calendar/ ) that uses OAuth2. It works well.

private IList<string> scopes = new List<string>(); private CalendarService calendarService; private void InitializeCalendarService() { // Add the calendar specific scope to the scopes list scopes.Add(CalendarService.Scopes.Calendar.GetStringValue()); // Display the header and initialize the sample CommandLine.EnableExceptionHandling(); CommandLine.DisplayGoogleSampleHeader("Google.Api.Calendar.v3 Sample"); // Create the authenticator //FullClientCredentials credentials = PromptingClientCredentials.EnsureFullClientCredentials(); var provider = new NativeApplicationClient(GoogleAuthenticationServer.Description); FullClientCredentials credentials = new FullClientCredentials(); credentials.ClientId = "XYZ.apps.googleusercontent.com"; credentials.ClientSecret = "XYZ"; credentials.ApiKey = "XYZ"; provider.ClientIdentifier = credentials.ClientId; provider.ClientSecret = credentials.ClientSecret; OAuth2Authenticator<NativeApplicationClient> auth = new OAuth2Authenticator<NativeApplicationClient>(provider, GetAuthorization); // Create the calendar service using an initializer instance BaseClientService.Initializer initializer = new BaseClientService.Initializer(); initializer.Authenticator = auth; calendarService = new CalendarService(initializer); CalendarList list = calendarService.CalendarList.List().Execute(); // do something with the list .. the list is all good } public IAuthorizationState GetAuthorization(NativeApplicationClient client) { // You should use a more secure way of storing the key here as // .NET applications can be disassembled using a reflection tool. const string STORAGE = "google.samples.dotnet.calendar"; const string KEY = "s0mekey"; // Check if there is a cached refresh token available. IAuthorizationState state = AuthorizationMgr.GetCachedRefreshToken(STORAGE, KEY); if ((state != null)) { try { client.RefreshToken(state); return state; // we are done } catch (DotNetOpenAuth.Messaging.ProtocolException ex) { CommandLine.WriteError("Using an existing refresh token failed: " + ex.Message); CommandLine.WriteLine(); } } // Retrieve the authorization from the user string[] array = new string[scopes.Count]; scopes.CopyTo(array,0); state = AuthorizationMgr.RequestNativeAuthorization(client, array); AuthorizationMgr.SetCachedRefreshToken(STORAGE, KEY, state); return state; } 

How can I use a similar OAuth2Authenticator to retrieve contacts?

I can get contacts using the code below, but not without a password, I need to get it to work using Oath2. The example below uses the contacts Gdata api v2. I can see that I can go through the OAuth2Authenticator, but I don’t know exactly how to do it correctly (I can’t see valid C # examples on google) and get an access code based on what the user selects. I can't figure out how to use OAuth2Authenticator with api v3 contacts ( https://developers.google.com/google-apps/contacts/v3/ )

 RequestSettings rsLoginInfo = new RequestSettings("", email,pwd); rsLoginInfo.AutoPaging = true; ContactsRequest cRequest = new ContactsRequest(rsLoginInfo); // fetch contacts list Feed<Contact> feedContacts = cRequest.GetContacts(); foreach (Contact gmailAddresses in feedContacts.Entries) { // Looping to read email addresses foreach (EMail emailId in gmailAddresses.Emails) { lstContacts.Add(emailId.Address); } } 

Answer 1

I ended up extracting the access code using a browser control that reads the value of the document title when the user selects the google account and grants access.

eg:

Generate url

 RedirectURI = "urn:ietf:wg:oauth:2.0:oob" OAuth2Parameters parameters = new OAuth2Parameters() { ClientId = clientId, ClientSecret = clientSecret, RedirectUri = redirectUri, Scope = requiredScope }; // Request authorization from the user (by opening a browser window): string url = OAuthUtil.CreateOAuth2AuthorizationUrl(parameters); var loginUri = new Uri(url); // This form has browser control GoogleLoginForm form = new GoogleLoginForm(loginUri, redirectUri); var dr = form.ShowDialog(); if (dr == System.Windows.Forms.DialogResult.OK) { parameters.AccessCode = form.OAuthVerifierToken; } 

Then in GoogleLoginForm: We have browser control and the registered browserControl_Navigated event, and do the following. The DocumentTitle contains an access code that is used to generate a token.

 private void GoogleLoginForm_Load(object sender, EventArgs e) { wbGoogleLogin.Url = _loginUri; } private void wbGoogleLogin_Navigated(object sender, WebBrowserNavigatedEventArgs e) { string fullPath = e.Url.ToString(); WebBrowser control = sender as WebBrowser; if (control != null && !string.IsNullOrEmpty(control.DocumentTitle) && control.DocumentTitle.Contains("Success code")) { _OAuthVerifierToken = control.DocumentTitle.Replace("Success code=",""); DialogResult = DialogResult.OK; } } 

Thus, this can be done in the same piece of code, without having to write a complex callback service to read the access token back into our system.

It’s not entirely clear why this is built into the api calendar, but the contacts API is not.

Answer 2

Firstly, a quick answer to your question. I believe that IAuthorizationState has similar properties for OAuth2Parameters. So you should do it (combining it with the code you have for the calendar):

 OAuth2Authenticator<NativeApplicationClient> auth = new OAuth2Authenticator<NativeApplicationClient>(provider, GetAuthorization); //This will call your GetAuthorization method auth.LoadAccessToken() RequestSettings settings = new RequestSettings("appName", auth.State.AccessToken); ContactsRequest cRequest = new ContactsRequest(settings); // fetch contacts list Feed<Contact> feedContacts = cRequest.GetContacts(); foreach (Contact gmailAddresses in feedContacts.Entries) { // Looping to read email addresses foreach (EMail emailId in gmailAddresses.Emails) { lstContacts.Add(emailId.Address); } } 

This should work, as RequestSettings allows you to specify an access token. However, I myself prefer to use:

 var parameters = new OAuth2Parameters() { //Client ClientId = CLIENT_ID, ClientSecret = CLIENT_SECRET, RedirectUri = redirectUri, Scope = "https://www.google.com/m8/feeds", ResponseType = "code" }; //User clicks this auth url and will then be sent to your redirect url with a code parameter var authorizationUrl = OAuthUtil.CreateOAuth2AuthorizationUrl(parameters); . . . //using the code parameter parameters.AccessCode = code; OAuthUtil.GetAccessToken(parameters); var settings = new RequestSettings(applicationName, parameters); var cr = new ContactsRequest(settings); //Now you can use contacts as you would have before 

Although, Ive only tested this with web server applications, so maybe an authenticator is needed for your situation? I found these source codes handy:

OAuth2Demo

IAuthorizationState

OAuth2Authenticator