public IActionResult GetValidateCode()
        {
            string validateString = ValidateCodeHelper.CreateVaildateString(4);

            byte[] buffer = ValidateCodeHelper.CreateValidateCode(validateString);
            string ip     = HttpContext.Connection.RemoteIpAddress.ToString();

            MemoryCacheHelper.SetCache(ip, validateString);
            return(File(buffer, @"image/png"));
        }