调用企业微信 回调接口

调用企业微信回调接口的一个GET方法。```

 [HttpGet]
        public HttpResponseMessage GetEhrLeaveApproveAsyncCallBack(string msg_signature, string timestamp, string nonce, string echostr)
        {
            var Ency = new WXBizMsgCrypt(Token, EncodingAESKey, cordid);
            string sVerifyEchoStr = echostr.Replace(" ", "+").Replace(" ", "+");//转换编码，将URL传过来的空格转换为+ 号
            int ret = 0;
            string sEchoStr = "";
            ret = Ency.VerifyURL(msg_signature, timestamp, nonce, sVerifyEchoStr, ref sEchoStr);
            var error = WXBizMsgCryptErrorCode(ret);
            SimpleLogHelper.LogFile("[GET企业微信回调接口信息,返回代码]" + ret + "[信息]" + error, "", SimpleLogHelper.TimingWebApi);
            HttpResponseMessage responseMessage = new HttpResponseMessage { Content = new StringContent(sEchoStr, Encoding.GetEncoding("UTF-8"), "text/plain") };
            return responseMessage;
        }