微信开发者形式调用的时候总显示token验证失败

  public void WxIndex()
        {
            //signature	 微信加密签名，signature结合了开发者填写的token参数和请求中的timestamp参数、nonce参数。
            //timestamp	 时间戳
            //nonce	 随机数
            //echostr	 随机字符串s

            string signature = HttpContext.Request["signature"];
            string timestamp = HttpContext.Request["timestamp"];
            string nonce = HttpContext.Request["nonce"];
            string echostr = HttpContext.Request["echostr"];


            string Token = "hgc2015";

            string[] wxstring = { Token, timestamp, nonce };

            Array.Sort(wxstring);

            string temp2 = string.Join("", wxstring);
            string TEMP3 = FormsAuthentication.HashPasswordForStoringInConfigFile(temp2, "SHA1");

            if (TEMP3.ToLower().Equals(signature))
            {
                Response.Write(echostr);
                Response.End();
            }
        }