// This is what called when button is clicked

Task t3 = new Task(SpawnTask);
            t3.Start();
            t3.Wait();

//if noofthreads are less 50 then GUI is woking fine.. if number increases then GUI takes much time for repaint.. where as other
//softwares are working without any problem even if the threads are more than 500!! in the same system
 public void SpawnTask()
        {
            try
            {
                ParallelOptions po = new ParallelOptions();
                po.CancellationToken = cts.Token;
                po.MaxDegreeOfParallelism = noofthreads;
                Parallel.ForEach(
                urls,
                po,
                url => checkpl(url));
            }
            catch (Exception ex)
            {

            }
        }


public void checkpl(string url)
        {

            try
    {
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
            request.Timeout = 60*1000;
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            string stext = "";
            using (BufferedStream buffer = new BufferedStream(response.GetResponseStream()))
            {
                using (StreamReader reader = new StreamReader(buffer))
                {
                    stext = reader.ReadToEnd();
                }
            }
            response.Close();
        if (stext .IndexOf("domainname.com") != -1)
            {
                tfound = tfound  + 1;
                string lext = "Total Found : "+tfound.ToString();
                label3.BeginInvoke(new InvokeDelegate(UpdateLabel), ltext);
                slist.Add(url);

                textBox2.BeginInvoke(new InvokeDelegate4(UpdateText), "Working Url " + url);

            }
    }
 catch (Exception ex)
            {

            }
        }