shell怎么判断文件是否存在 c#判断远程文件是否存在

c#判断远程文件是否存在  

　　// :    public static bool IsExist(string uri)            {                HttpWebRequest req = null;                HttpWebResponse res = null;                try                {                    req = (HttpWebRequest)WebRequest Create(uri);                    req Method = HEAD ;                    req Timeout = ;                    res = (HttpWebResponse)req GetResponse();                    return (res StatusCode == HttpStatusCode OK);                }                catch                {                    return false;                }                finally                {                    if (res != null)                    {                        res Close();                        res = null;                    }                    if (req != null)                    {                        req Abort();                        req = null;                    }                }            }

　　// :

　　private bool UrlExistsUsingXmlHttp(string url)    {      //注意 此方法需要引用Msxml dll      MSXML XMLHTTP _xml();      _xml open( HEAD url false null null);      _xml send( );      return (_xml status == );    }