Sing signature algorithm

On a project to use signing algorithm, the interface is written like this:

5.1.1 Input parameters 
Method = openapi.stockout.create 
timestamp = , 2015 - 04 - 26 is  00 : 00 : 07 
the format = XML 
app_key = testerp_appkey 
V = 2.0 
sign_method = MD5 
the customerId = Test
 5.1.2 . Alphabetical ascending 
app_key = testerp_appkey 
the customerId = cust- Stub- code 
the format = XML 
Method = openapi.stockout.create
sign_method = MD5 
timestamp = , 2015 - 04 - 26 is  00 : 00 : 07 
V = 2.0 
5.1.3 connection string. 
connection parameter names and parameter values, and inclusive plus Secret, assumed here Secret = Test, as follows: 
testapp_keytesterp_appkeycustomerIdstub - cust- codeformatxmlmethod 
openapi.stockout.createsign_methodmd5timestamp2015 - 04 - 26 is  00 : 00 .: 07v2 0 body Test
 wherein: body with body data request instead
 5.1.4 generate the signature Sign.
 32 uppercase MD5 value ->D06D88CB34B2EC0E5C9BAB396C9542B6
 5.1.5 . Assembling the URL request 
to convert all parameter values UTF -8 encoding , then assembled, and the ENCODING URL as follows: 
HTTP: // sandbox.vwms.cn/open/service?method= 
opeanapi.stockout.create & timestamp = 2015 - 04 -
 26 % 2000 : 00 : 07 & format = xml & app_key = testerp_appkey & v = 2.0 & Sign = D06D88CB34B2EC0E5C9B 
AB396C9542B6 & sign_method = MD5 & customerId Stub-cust-code =

Practice is this:

 //timestamp
                    string timestamp = DateTime.Now.ToString();
                    JObject o = new JObject(
                         new JProperty("app_key", _Setting.Value.app_key.ToString()),
                         new JProperty("customerId", _Setting.Value.customerId.ToString()),
                         new JProperty("format", "xml"),
                         new JProperty("method", " Openapi.singleitem.synchronize " ),
                          new new JProperty ( " sign_method " , " MD5 " ),
                          new new JProperty ( " timestamp " , timestamp),
                          new new JProperty ( " V " , " 2.0 " ) 
                        ); 

                    // put above sort 
                    String S = JsonConvert.SerializeObject (O); 
                    the Dictionary <string, string> values = JsonConvert.DeserializeObject<Dictionary<string, string>>(s);
                    string Sort_Ret = CommonData.GetSignature(values, "");
                    //拼接URL链接
                    string secret = _Setting.Value.secret;
                    string Sign = CommonData.StrToMD5(secret + Sort_Ret + in0 + secret);
                    string url = "" + _Setting.Value.UrlApi.ToString() + "?" +
                     "method=" + "openapi.singleitem.synchronize" +
                     "&timestamp=" + timestamp + "" +
                     "&format=xml" +
                     "&app_key=" + _Setting.Value.app_key.ToString() + "" +
                     "&v=2.0" +
                     "&sign=" + Sign + "" +
                     "&sign_method=md5" +
                     "&customerId="_Setting.Value.customerId.ToString + () + "" ;
                     // send Http request 
                    HttpClient Client = httpClientFactory.CreateClient ();
                    HttpContent Content = new new StringContent object, (IN0, Encoding.UTF8 , "file application / JSON"); // The ownership of utf-8 encoded
                     var RET = the await client.PostAsync (URL, Content);
                     var RR = the await ret.Content.ReadAsStringAsync ();

The method involved, is a sort of a Sign value is obtained

 public  static  String GetSignature (the IDictionary < String , String > Parameters, String Secret) 
        { 
            // first parameter lexicographical sort ascending its parameter name 
            the IDictionary < String , String > = sortedParams new new the SortedDictionary < String , String > (Parameters) ; 
            the IEnumerator <KeyValuePair < String , String >> Iterator = sortedParams.GetEnumerator (); 

            // traversing the dictionary sorted, all the parameters as "keyvaluekeyvalue" formats are spliced together 
            StringBuilder basestring =new StringBuilder();
            while (iterator.MoveNext())
            {
                string key = iterator.Current.Key;
                string value = iterator.Current.Value.ToString();
                if (!string.IsNullOrEmpty(key) && value != null)
                {
                    basestring.Append(key).Append(value);
                }
            }

            // 使用MD5对待签名串求签
            //string upperCaseStr = StrToMD5(basestring.ToString());
            //string result = StrToMD5(upperCaseStr + secret);
            return basestring.ToString();
        }

        public static string StrToMD5(string str)
        {
            byte[] data = Encoding.UTF8.GetBytes(str);
            MD5 md5 = new MD5CryptoServiceProvider();
            byte[] OutBytes = md5.ComputeHash(data);

            string OutString = "";
            for (int i = 0; i < OutBytes.Length; i++)
            {
                OutString += OutBytes[i].ToString("x2");
            }
            return OutString.ToUpper();
        }

        public static DateTime GetLocaltime(string StandardTime)
        {
            var ChTimeZone = TimeZoneInfo.FindSystemTimeZoneById(StandardTime);
            DateTime ChTime = TimeZoneInfo.ConvertTime(DateTime.Now, TimeZoneInfo.Local, ChTimeZone);
           
            return ChTime;
        }