private string GetKey(string areaId, string type, string date, string appId, string privateKey)        {            var hmac = HMACSHA1.Create();            var publicKey = GetPublicKey(areaId, type, date, appId);            var data =http://www.mamicode.com/ System.Text.Encoding.UTF8.GetBytes(publicKey);            //密钥            var key = System.Text.Encoding.UTF8.GetBytes(privateKey);            hmac.Key = key;            //对数据进行签名            var signedData =http://www.mamicode.com/ hmac.ComputeHash(data);            return Convert.ToBase64String(signedData);        }        private string GetPublicKey(string areaId, string type, string date, string appId)        {            return string.Format("http://open.weather.com.cn/data/?areaid={0}&type={1}&date={2}&appid={3}", areaId, type, date, appId);        }        /// <summary>        /// 获取请求URL        /// </summary>        /// <param name="areaId">地区ID，例：北京=101010100</param>        /// <param name="type">预警:alarm 实况:observe 指数:index 常规预报(24小时):forecast1d</param>        /// <param name="date">日期,年月日时分,例：201410091040</param>        /// <param name="appId"></param>        /// <param name="privateKey"></param>        /// <returns></returns>        public string GetUrl(string areaId, string type, string date, string appId, string privateKey)        {            string key = GetKey(areaId, type, date, appId, privateKey);            return string.Format("http://open.weather.com.cn/data/?areaid={0}&type={1}&date={2}&appid={3}&key={4}",              areaId, type, date, appId.Substring(0, 6), HttpUtility.UrlEncodeUnicode(key));        }