数据字典内的key按照字典排序，常见于加密算法中

        /// <summary>
        /// 数据字典内的key按照字典排序，常见于加密算法中
        /// </summary>
        private static string sortKey(Dictionary<string, object> param)
        {
            StringBuilder str = new StringBuilder();
            var keys = param.Keys.OrderBy(u => u).ToList();
            foreach(string key in keys)
            {
                object value = param[key];
                if (value != null && !string.IsNullOrWhiteSpace(value.ToString()))
                {
                    str.Append(string.Format("{0}={1}&",key,value.ToString()));
                }
            }
            if (str.Length > 0)
                str = str.Remove(str.Length-1,1);
            return str.ToString();
        }