Google OAuth2 API

我在设置Google api oauth2以访问日历api时遇到问题。我在下面使用了以下代码，它可以正常工作，并提示用户授予对日历api的访问权限。但是，一旦用户允许访问，该站点就会在重定向循环中结束，在调试时，结果将显示为空。凭据始终为null。使用提琴手，我可以看到正在从以下网址接收令牌：account.google.com/o/oauth2/token

具有以下响应：

{
  "access_token" : "TOKEN",
  "token_type" : "Bearer",
  "expires_in" : 3600
}

我完全为为什么从来没有填充凭据而感到困惑。这是我正在使用的代码：

public class AppFlowMetadata : FlowMetadata
{
    private static readonly IAuthorizationCodeFlow flow =
        new GoogleAuthorizationCodeFlow(new GoogleAuthorizationCodeFlow.Initializer
        {
            ClientSecrets = new ClientSecrets
            {
                ClientId = "CLIENT_ID",
                ClientSecret = "CLIENT_SECRET"
            },
            Scopes = new[] { CalendarService.Scope.Calendar }
        });

    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();

    }

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




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

public class GoogleController : Controller
{
    // GET: Google
    [Route("google")]
    public ActionResult Index(CancellationToken cancellationToken)
    {
        //try to get results
        var result = new AuthorizationCodeMvcApp(this, new AppFlowMetadata()).
                        AuthorizeAsync(cancellationToken).Result;


        if (result.Credential != null)
        {
            //// This bit checks if the token is out of date, 
            //// and refreshes the access token using the refresh token.
            if (result.Credential.Token.IsExpired(SystemClock.Default))
            {
                Google.Apis.Auth.OAuth2.Responses.TokenResponse token = new Google.Apis.Auth.OAuth2.Responses.TokenResponse();
                //If the token is expired recreate the token
                token = result.Credential.Flow.RefreshTokenAsync("1", result.Credential.Token.RefreshToken, CancellationToken.None).Result;

                //Get the authorization details back
                result = new AuthorizationCodeMvcApp(this, new AppFlowMetadata()).AuthorizeAsync(cancellationToken).Result;
            }
            var service = new CalendarService(new BaseClientService.Initializer
                {
                    HttpClientInitializer = result.Credential,
                    ApplicationName = "ASP.NET MVC Sample"
                });

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