HttpWebResponse in Thread throws Forbidden

I would like to call multiple times to a web resource, however I get forbidden when asking the webresponse.

protected void Page_Load(object sender, EventArgs e)
    {


        Thread[] tt = new Thread[10];
        for (int i = 0; i < 10; i++)
        {            
            Thread t = new Thread(doJob);
            tt[i] = t;
            t.Start();
        }

        foreach (Thread t in tt)
        {
            t.Join();
        }
        Response.Write("TOTAL" + howmanyDone);
    }

    private void doJob()
    {        
        HttpWebRequest wr = (H开发者_如何学编程ttpWebRequest) HttpWebRequest.Create("http://www.google.com");        
        WebResponse res = wr.GetResponse();

There's a default limit of 2 simultaneous requests to the same domain built into the framework. Just put this line of code into your code after you've created the HttpWebRequest object:

wr.ServicePoint.ConnectionLimit = 50;

Check out the docs: http://msdn.microsoft.com/en-us/library/kd5csyhf.aspx