private string RetrieveAccessToken(string authorizationCode) { var appId = GetAppId(); var appSecret = GetAppSecret(); var returnUriValue = BuildCallbackUriValue(); var param = new NameValueCollection { { "client_id", appId }, { "client_secret", appSecret }, { "code", authorizationCode }, { "grant_type", "authorization_code" }, { "redirect_uri", returnUriValue }, }; var url = OAuthHelpers.BuildUri(OAuthUrl, "o/oauth2/token", new NameValueCollection()); string accessToken = OAuthHelpers.GetObjectWithPost(url, param).access_token; return(accessToken); }