public IActionResult GetPDFFile()
        {
            byte[] buffer = _fileAppService.GetPDFFile();

            if (buffer != null)
            {
                HttpContext.Response.ContentType = "application/pdf";
                HttpContext.Response.Headers.Add("content-length", buffer.Length.ToString());
                HttpContext.Response.Body.Write(buffer, 0, buffer.Length);
            }
            return(new ContentResult());
        }
        public IActionResult Get()
        {
            var buffer = _fileAppService.GetPDFFile();

            //if(buffer != null){
            //    HttpContext.Response.ContentType = "application/pdf";
            //    HttpContext.Response.Headers.
            //    HttpContext.Response.Headers.Add("content-length", buffer.Length.ToString());
            //    HttpContext.Response.Body.Write(buffer, 0, buffer.Length);
            //}
            return(File(buffer, GetContentType("xxx.pdf"), "pdf"));
        }