在为RequestToken调用Google API时出现签名无效错误

Question

我正在为RequestToken调用Google API，而我正在使用OAuhtBase生成我的签名。我的代码如下：

 public Uri BaseURL
        {
            get { return new Uri("https://www.google.com/accounts/OAuthGetRequestToken");  }
            set { }
        }
        public string ConsumerKey
        {
            get { return "anonymous"; }
        }
        public string Nonce
        {
            get { return oAuthBase.GenerateNonce(); }
        }
        public string SignatureMethod
        {
            get { return "HMAC-SHA1"; }
        }
        public string Signature { get
        {
            string url;
            string requestParams;
            return HttpUtility.UrlEncode(oAuthBase.GenerateSignature(BaseURL, ConsumerKey, ConsumerSecret, string.Empty, string.Empty,
                                               "GET", Timestamp, Nonce, out url, out requestParams));
        }
        }
        public string Timestamp
        {
            get { return oAuthBase.GenerateTimeStamp(); }
        }
        public string Scope
        {
            get { return "https://www.googleapis.com/auth/userinfo.profile"; }
        }
        public string Callback
        {
            get { return "www.contestfactory.com"; }
        }


          public string GenerateURL()
          {

             var returnURL = new StringBuilder(BaseURL.ToString());

             returnURL.Append("?");
             returnURL.Append("oauth_consumer_key=" + ConsumerKey);
             returnURL.Append("&oauth_signature_method=" + SignatureMethod);
             returnURL.Append("&oauth_signature=" + Signature);
             returnURL.Append("&oauth_timestamp=" + Timestamp);
             returnURL.Append("&oauth_nonce=" + Nonce);
             returnURL.Append("&oauth_callback=" + Callback);
             returnURL.Append("&scope=" + Scope);

              return returnURL.ToString();

          }

现在，当我的javascript尝试浏览到此代码生成的URL时。它在浏览器上返回以下错误：

  

signature_invalid   base_string：GET＆安培; HTTPS％3A％2F％2Fwww.google.com％2Faccounts％2FOAuthGetRequestToken＆安培; oauth_callback％3Dwww.contestfactory.com％26oauth_consumer_key％3Danonymous％26oauth_nonce％3D400857％26oauth_signature_method％3DHMAC-SHA1％26oauth_timestamp％3D1334790691％26scope％3Dhttps％ 253A％252F％252Fwww.googleapis.com％252Fauth％252Fuserinfo.profile

我不确定签名的哪一部分可能是错误的，因为我传递了所有必需的参数，它们都是基本的字符串。任何想法？