/// <summary>
        /// 判断一个字符串是否为url
        /// </summary>
        /// <param name="str"></param>
        /// <returns></returns>
        public static bool IsUrl(string str)
        {
            try
            {
                string Url = @"^http(s)?://([\w-]+\.)+[\w-]+(/[\w- ./?%&=]*)?$";
                return Regex.IsMatch(str, Url);
            }
            catch (Exception ex)
            {
                return false;
            }
        }