SmartWeatherAPI_Lite_WebAPI C# 获取key加密

 string GetKey(string appid, string privateKey, string areaId, string date, string type)
        {
            //使用SHA1的HMAC

            HMAC hmac = HMACSHA1.Create();
            var publicKey = "http://webapi.weather.com.cn/data/?areaid={0}&type={1}&date={2}&appid={3}";
            var data = System.Text.Encoding.UTF8.GetBytes(string.Format(publicKey, areaId, type, date, appid));
            //密钥
            var key = System.Text.Encoding.UTF8.GetBytes(privateKey);
            hmac.Key = key;

            //对数据进行签名
            var signedData = hmac.ComputeHash(data);
            return Convert.ToBase64String(signedData);

        }