Can I use Google APIs with MVC 5 Authentication via Google instead of using Google's OAuth 2.0? - asp.net-mvc-5

Question

Note, that I have previously written an MVC app according to Google Guidelines, by first setting up a project in Google Developers Console, providing Google Auth 2.0 authentication. Everything worked (not perfect though), but worked.
The Client ID and Client Secret I placed in Web.config. Therefore only one specific user could get his information. But I wanted any user to be able to get
his gmail message and calendar events, so we need this general Authentication model, like the one implemented in MVC 5 as Google Sign-in button. MVC 5 provides built-in functionality to sign in via Google, Facebook, Twitter, etc.
After you sign in via Google option, is it possible to access Google APIs, such as Calendar, Gmail, etc. to get my own events, gmail messages?
Example, I want to get Gmail message, I have this class:
public static MyGmail GetGmail(UserCredential credential)
{
var mygmail = new MyGmail();
var service = new GmailService(new BaseClientService.Initializer { HttpClientInitializer = credential });
var request = service.Users.Messages.List("me");
request.Q = "in:inbox is:unread";
var messages = request.Execute().Messages;
return mygmail;
}
Notice this line?
var service = new GmailService(new BaseClientService.Initializer { HttpClientInitializer = credential });
I need to pass credential to that service.
So I have this action in my controller:
public ActionResult Gmail()
{
return PartialView(GmailManager.GetGmail(result.Credential));
}
Notice this parameter: result.Credential?
That is the credentials.
That result object is coming from the Index Action:
public async Task<ActionResult> Index(CancellationToken cancellationToken)
{
if (result == null || result.Credential == null)
{
result = await new AuthorizationCodeMvcApp(this, new AppFlowMetadata()).AuthorizeAsync(cancellationToken);
if (result.Credential == null) return new RedirectResult(result.RedirectUri);
result.Credential.Token.ExpiresInSeconds = expiresInSeconds;
result.Credential.Token.RefreshToken = refreshToken;
}
return View();
}
Notice this line?
result = await new AuthorizationCodeMvcApp(this, new AppFlowMetadata()).AuthorizeAsync(cancellationToken);
The result object is defined like this:
private static AuthorizationCodeWebApp.AuthResult result;
This is how Google OAuth 2.0 works. I am not putting here the AuthCallbackController code for simplicity. Who know what I am talking about and have seen Google Developers Tutorial on authenticating via Google OAuth 2.0, he will understand.
The idea is that after the Authentication (or when you already have the Auth token) you get that result object that has result.Credential property that I can pass as parameter to Google API Service (Gmail, Calendar or any other service) and the authenticated user can retrieve his own gamail messages or calendar events.
Now, to the question - since Authentication via 3-rd party providers such as Google is a part of MVC 5 functionality, the OWIN Katana, Microsoft Implementation (the Google button you can click and Authenticate), I dont need Google OAuth 2.0 code to authenticate a user.
That brings me to the problem - since there is no Google OAuth 2.0 implementation here, I will not be able to get that result object with Credentials, that I need to pass as parameter to Google API service.
But the user is Authenticated already via Google, so that should be double to call Google API Service, just dont know how?
Any ideas? Thanks

Answer 1

I guess not :)) Since there is no AuthorizationCodeWebApp.AuthResult object, that contains result.Credentials that is required to be passed as parameter to Google API Service:
var service = new GmailService(new BaseClientService.Initializer {
HttpClientInitializer = credential });
where credential is of type UserCredential (the one that comes back after Google OAuth2 authorization: AuthorizationCodeWebApp.AuthResult.Credential)