public partial class Weixin : System.Web.UI.Page
    {
        private string Token = "weixin";        //与那边填写的token一致

        protected void Page_Load(object sender, EventArgs e)
        {
            if (Request.HttpMethod.ToLower() == "post")
            {
                ResMsg();
            }
            else
            {
                Valid();
            }
        }

        /// <summary>
        /// 验证微信签名
        /// </summary>
        /// * 将token、timestamp、nonce三个参数进行字典序排序
        /// * 将三个参数字符串拼接成一个字符串进行sha1加密
        /// * 开发者获得加密后的字符串可与signature对比，标识该请求来源于微信。
        /// <returns></returns>
        private bool CheckSignature()
        {
            string signature = Request.QueryString["signature"];
            string timestamp = Request.QueryString["timestamp"];
            string nonce = Request.QueryString["nonce"];
            string[] ArrTmp = { Token, timestamp, nonce };
            Array.Sort(ArrTmp);     //字典排序
            string tmpStr = string.Join("", ArrTmp);
            tmpStr = FormsAuthentication.HashPasswordForStoringInConfigFile(tmpStr, "SHA1");
            tmpStr = tmpStr.ToLower();
            if (tmpStr == signature)
            {
                return true;
            }
            else
            {
                return false;
            }
        }

        private void Valid()
        {
            string echoStr = Request.QueryString["echoStr"];
            if (CheckSignature())
            {
                if (!string.IsNullOrEmpty(echoStr))
                {
                    Response.Write(echoStr);
                    Response.End();
                }
            }
        }       
    }