XML文件绑定数据集控件操作

//数据绑定
    public void DataBind()
    {
        DataSet ds = new DataSet();
        ds.ReadXml(Server.MapPath(@"App_data/dbGuest.xml"));
        GridView1.DataSource = ds.Tables[0].DefaultView;
        GridView1.DataBind();
    }
//添加
   public void XmlDataAdd()
    {
        DataSet ds = new DataSet();
        ds.ReadXml(Server.MapPath(@"App_data/dbGuest.xml"));
        DataRow dr = ds.Tables[0].NewRow();
        dr["Name"] = "spark";
        dr["City"] = "tokyo";
        dr["Email"] = "jis@163.com";
        dr["Message"] = "thank you";
        dr["STime"] = DateTime.Now.ToString();
        ds.Tables[0].Rows.Add(dr);
        ds.WriteXml(Server.MapPath(@"App_data/dbGuest.xml"));
    }
dbGuest.xml
<?xml version="1.0" standalone="yes"?>
<dbGuest xmlns="http://tempuri.org/dbGuest.xsd">
  <User>
    <Name>shaoazhd</Name>
    <City>beijing</City>
    <Email>sss@22.net</Email>
    <Message>afsa</Message>
  </User>
  <User>
  &