public ActionResult GuestUpload(HttpPostedFileBase fileData)
        {
           
            if (fileData != null)
            {
                try
                {
                    // 文件上传后的保存路径
                    string filePath = Server.MapPath("~/GuestBookUpload/");
                    if (!Directory.Exists(filePath))
                    {
                        Directory.CreateDirectory(filePath);
                    }
                    string fileName = Path.GetFileName(fileData.FileName);// 原始文件名称
                    string fileExtension = Path.GetExtension(fileName); // 文件扩展名
                    string saveName = Guid.NewGuid().ToString() + fileExtension; // 保存文件名称
                    fileData.SaveAs(filePath + saveName);


                    return Json(new { Success = true, fileData = fileData });
                }
                catch (Exception ex)
                {
                    return Json(new { Success = false, Message = ex.Message }, JsonRequestBehavior.AllowGet);
                }
            }
            else
            {

                return Json(new { Success = false, Message = "请选择要上传的文件！" }, JsonRequestBehavior.AllowGet);
            }
        }