Process调用BeginOutputReadLine()后如何让主线程响应啊.. 求助.

Question

先贴代码         /// <summary>
        /// 执行 宽带 挂断 与连接
        /// </summary>
        /// <param name="cmds"></param>
        private void cmdExecute(List<String> cmds)
        {
            Process p = new Process();
            p.StartInfo.FileName = "cmd.exe";
            p.StartInfo.UseShellExecute = false;
            p.StartInfo.RedirectStandardInput = true;
            p.StartInfo.RedirectStandardOutput = true;
            //p.StartInfo.RedirectStandardError = true;
            p.StartInfo.CreateNoWindow = true;            p.EnableRaisingEvents = true;
            p.Exited += new EventHandler(p_Exited);//线程退出
            p.OutputDataReceived += new DataReceivedEventHandler(p_OutputDataReceived);//异步监听输出信息
            //p.ErrorDataReceived += new DataReceivedEventHandler(p_ErrorDataReceived);//异步监听错误信息
        //try{    
            p.Start();
            for (Int32 i = 0; i < cmds.Count; i++)
            {
                p.StandardInput.WriteLine(cmds[i]);
            }
            p.BeginOutputReadLine();
            //p.BeginErrorReadLine();
            //String error = p.StandardError.ReadToEnd();//标记1 : 这里必然要出错 
            p.StandardInput.WriteLine("exit");
            p.WaitForExit();
            p.Close();
          //}
        //catch{}
        }
        /// <summary>
        /// 委托..  利用这个操作主线程中的控件
        /// </summary>
        public delegate void OutputDataReceived(Object sender, DataReceivedEventArgs e);
        void p_OutputDataReceived(Object sender, DataReceivedEventArgs e)
        {
            try
            {
                if (this.InvokeRequired)
                {
                    OutputDataReceived o = new OutputDataReceived(p_OutputDataReceived);
                    Invoke(o, new Object[] { sender, e });//标记2
                }
                else
                {
                    richTextBox1.AppendText(e.Data);
                    richTextBox1.AppendText("\n");
                }
            }
            catch (Exception mes)
            {
                MessageBox.Show(mes.ToString()+"//线程异常");
            }
        }问题就出在上面这 段里面.. 如果 把cmdExecute中的 try 打开 吧标记1位置注释打开 不处理错误
主线程里的控件 richTextBox1能正常显示返回的信息.. 界面也不会卡住..
这当然是不允许的.. 不能同时 异步和同步操作StandardOutput.. 
如果就上面这段代码执行. 能执行完 但是主线程一直在p.WaitForExit();  求高手救命啊.. 刚开始winform 什么都不懂...