public static Task <string> GetAuthUrlAsync(ResumptionCookie resumptionCookie, string resourceId) { // https://start.exactonline.nl/api/oauth2/auth?client_id=01b85808-0248-47a8-9f25-08acd900f788&redirect_uri=http://www.mstack.nl&response_type=code&force_login=0&state=test var settings = AuthenticationSettings.GetFromAppSettings(); string stateParameter = AuthUtilities.EncodeResumptionCookie(resumptionCookie); NameValueCollection queryParams = new NameValueCollection(); queryParams.Add("client_id", settings.ClientId); queryParams.Add("redirect_uri", settings.RedirectUrl); queryParams.Add("response_type", "code"); queryParams.Add("force_login", "0"); queryParams.Add("state", stateParameter); string queryString = AuthUtilities.ToQueryString(queryParams); string result = "https://start.exactonline.nl/api/oauth2/auth" + queryString; return(Task.FromResult(result)); }