请诸位老师同仁帮忙看一下代码

请各位老师同仁帮忙看一下代码
本帖最后由 yyy8343 于 2014-01-01 18:32:35 编辑 代码如下：
public partial class MainPage : PhoneApplicationPage
    {
        HttpWebRequest request = null;
        HttpWebResponse response = null;
        // 构造函数
        public MainPage()
        {
            InitializeComponent();
            string uri="http://fpad.ce.cn/hg/news_list.xml";

            request = (HttpWebRequest)WebRequest.Create(uri);
            request.Method = "POST";
            request.BeginGetResponse(new AsyncCallback(GetResponseCallBack), null);
        }

        private void GetResponseCallBack(IAsyncResult ar)
        {
            List<News> newList = new List<Finace.News>();

            response = (HttpWebResponse)request.EndGetResponse(ar);
            using (Stream stream = response.GetResponseStream())
            {
                StreamReader reader = new StreamReader(stream,new Gb2312Encoding());

                using (XmlReader xmlReader = XmlReader.Create(reader))
                {
                    string title = "";
                    string intro = "";

                    while (xmlReader.Read())
                    {
                        try
                        {
                            if (xmlReader.ReadToFollowing("a"))
                            {
                                title = xmlReader.ReadElementContentAsString();
                            }
                            if (xmlReader.ReadToFollowing("summary"))
                            {
                                intro = xmlReader.ReadElementContentAsString();
                            }
                        }
                        catch(Exception ex)
                        {
                            MessageBox.Show(ex.ToString());
                        }

                        if (title != "" || intro != "")

                        {
                            newList.Add(new News { Title = title, Intro = intro });
                        }
                    }
                    
                }                
            }
            Dispatcher.BeginInvoke(() =>
            {
                NewsList.ItemsSource = newList;
            });
        }
    }

    class News
    {
        public string Title { set; get; }
        public string Intro { set; get; }
    }

不管标题内容是什么，每次单步调试到第三条时就报错，就是说xml中的前两条数据都能读取成功，到第三条if (xmlReader.ReadToFollowing("a"))就被catch了
[解决办法]
要求16进制，但你输入的是 . 
所以无效。