Multithreading InvalidOperationException C#

我有一个按钮。当我点击这个按钮时，我创建了一个新线程然后转到ThreadProcSafe方法，我想在那里将响应设置到richtextbox中。但是当我试着做的时候我总是用InvalidOperationException告诉我cross线程操作无效:从其他线程访问的控件创建它的线程。有什么建议吗?

 delegate void SetTextCallback(string text);

    private Thread demoThread = null;
   private void Go_Click(object sender,EventArgs e)
    {
        this.demoThread =new Thread(new ThreadStart(this.ThreadProcSafe));
        this.demoThread.Start();
    }


    // This method send a request get response
    private void ThreadProcSafe()
    {
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
        HttpWebResponse response = (HttpWebResponse)request.GetResponse();
        StreamReader sr = new StreamReader(response.GetResponseStream());
        richTextBox1.Text = sr.ReadToEnd();
        sr.Close();
        this.SetText(richTextBox1.Text);
    }

   private void SetText(string text)
    {
        // InvokeRequired required compares the thread ID of the
        // calling thread to the thread ID of the creating thread.
        // If these threads are different, it returns true.
        if (this.richTextBox1.InvokeRequired)
        {
            SetTextCallback d = new SetTextCallback(SetText);
            this.Invoke(d, new object[] { text });
        }
        else
        {
            this.richTextBox1.Text = text;
        }
    }

private void ThreadProcSafe()
{
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
    HttpWebResponse response = (HttpWebResponse)request.GetResponse();
    StreamReader sr = new StreamReader(response.GetResponseStream());
    string res = sr.ReadToEnd();
    sr.Close();
    this.SetText(res);
}