判断远程文件是否存在

        private bool RemoteFileExists(string fileUrl)
        {
            try
            {
                HttpWebRequest re = (HttpWebRequest)WebRequest.Create(fileUrl);
                HttpWebResponse res = (HttpWebResponse)re.GetResponse();
                if (res.ContentLength != 0)
                {
                    //MessageBox.Show("文件存在");
                    return true;
                }
            }
            catch (Exception)
            {
                //MessageBox.Show("无此文件");
                return false;
            }
            return false;
        }