新建商品时，导入商品，随机文件名称的形成

  //随机文件名称
    public static string getRandomFileName(string fileName)
    {
        if (!string.IsNullOrEmpty(fileName))
        {
            System.Threading.Thread.Sleep(100);
            string fileType = fileName.Substring(fileName.LastIndexOf("."));
            System.Random rand = new System.Random();
            DateTime now = DateTime.Now;
            string str = "";
            str += now.Year.ToString();
            str += now.Month.ToString();
            str += now.Day.ToString();
            str += now.Hour.ToString();
            str += now.Minute.ToString();
            str += now.Second.ToString();
            str += rand.Next(0, 1000);
            return str + fileType;
        }
        else
        {
            return "";
        }
    }