//1:
    public static bool IsExist(string uri)
            {
                HttpWebRequest req = null;
                HttpWebResponse res = null;
                try
                {
                    req = (HttpWebRequest)WebRequest.Create(uri);
                    req.Method = "HEAD";
                    req.Timeout = 100;
                    res = (HttpWebResponse)req.GetResponse();
                    return (res.StatusCode == HttpStatusCode.OK);
                }
                catch
                {
                    return false;
                }
                finally
                {
                    if (res != null)
                    {
                        res.Close();
                        res = null;
                    }
                    if (req != null)
                    {