“现有连接被远程主机c＃强行关闭”

Question

我收到此代码的异常错误，我在windows应用程序中创建了这个表单，代码是自动登录到站点并下载文件，并将其存储在一个文件夹中，同时调试我得到异常错误为“基础连接已关闭：发送时发生意外错误。”内部异常是“现有连接被远程主机c＃强行关闭”

private void Form1_Load(object sender, EventArgs e)
    {

        try
        {
            string formUrl = "https://secure.gmail.com/account/doLogin.html?icmp=HO_LOGIN_BANNER"; // NOTE: This is the URL the form POSTs to, not the URL of the form (you can find this in the "action" attribute of the HTML's form tag
            string formParams = string.Format("username={0}&password={1}", "username", "password");
            string cookieHeader;
            WebRequest req = WebRequest.Create(formUrl);
            req.ContentType = "application/x-www-form-urlencoded";
            req.Method = "POST";
            byte[] bytes = Encoding.ASCII.GetBytes(formParams);
            req.ContentLength = bytes.Length;

            using (Stream os = req.GetRequestStream())
            {
                os.Write(bytes, 0, bytes.Length);
            }

            WebResponse resp = req.GetResponse();
            cookieHeader = resp.Headers["Set-cookie"];


            string pageSource;
            string getUrl = "https://secure.gmail.com/account/summary.html";
            WebRequest getRequest = WebRequest.Create(getUrl);
            getRequest.Headers.Add("Cookie", cookieHeader);
            WebResponse getResponse = getRequest.GetResponse();
            using (StreamReader sr = new StreamReader(getResponse.GetResponseStream()))
            {
                pageSource = sr.ReadToEnd();

            }

            WebClient Client = new WebClient();
            Client.DownloadFile("https://secure.gmail.com.com/account/callActivity/print.csv?lineNumber=16145838755&startDate=MNTH2014-04-24&fragment=true", @"C:\Downloads");
        }

        catch(Exception ex)
        {
            throw ex;
        }
    }
  }
}