多线程HtttpRequest 一定要记得关闭reponse

public static bool WebFileExistsWithClose(string url, int timeoutSeconds)
{
    HttpWebResponse response = null;
    bool flag;
    try
    {
        HttpWebRequest request = (HttpWebRequest) WebRequest.Create(url);
        request.Timeout = timeoutSeconds * 1000；

       request.AllowAutoRedirect = true;
        request.MaximumAutomaticRedirections = 200;
        response = (HttpWebResponse) request.GetResponse();
        if (response.StatusCode == HttpStatusCode.OK)
        {
            return true;
        }
        flag = false;
    }
    catch (WebException)
    {
        flag = false;
    }
    catch (Exception exception)
    {
        throw exception;
    }
    finally
    {
        if (response != null)
        {
            response.Close();
        }
    }
    return flag;
}