xero c＃“当前TokenRepository没有当前请求令牌”

Question

已设法连接到xero API并获取请求令牌。但是在重新启动项目（用于调试）之后，它主要在请求访问令牌时出现以下错误

The current TokenRepository doesn't have a current request token

根据我的理解和观察，错误是随机提出的。即有时它显示，有时它不会。相关代码如下：

public class HomeController : Controller
    {

        IOAuthSession oauthSession = ServiceProvider.GetCurrentSession();
        //
        // GET: /Home/


        public ActionResult XeroConnect()
        {
            Session.Clear();

            Repository repository = ServiceProvider.GetCurrentRepository();

            oauthSession.MessageLogger = new DebugMessageLogger();


            // Can we already access an organisation??
            if (oauthSession.HasValidAccessToken && repository != null && repository.Organisation != null)
            {
                return new RedirectResult("~/");
            }

            if (oauthSession is XeroApiPrivateSession)
            {
                throw new ApplicationException("The current private session cannot access the authorised organisation. Has the access token been revoked?");
            }


            var callbackUri = new UriBuilder(Request.Url.Scheme, Request.Url.Host, Request.Url.Port, "Home/Callback");
            RequestToken requestToken = oauthSession.GetRequestToken(callbackUri.Uri);

        string authorisationUrl = oauthSession.GetUserAuthorizationUrl();

            return new RedirectResult(authorisationUrl);
        }

        public ActionResult Callback()
        {
            string verificationCode = Request.Params["oauth_verifier"];
            AccessToken accessToken = oauthSession.ExchangeRequestTokenForAccessToken(verificationCode); // error shows here

            GetAndStoreAuthorisedOrganisationName();

            Repository repository = ServiceProvider.GetCurrentRepository();

           List<XeroApi.Model.Invoice> invoices = (from invoice in repository.Invoices
                          where invoice.LineItems.Count > 0
                          select invoice).ToList();

            return View(invoices);
        }
}

任何帮助表示赞赏。我也在要求新的请求令牌之前清除会话。