請求並操作指定url處的xml文件

HttpWebRequest hr = (HttpWebRequest)WebRequest.Create(url);//向回返回xml文件的網址發送http請求
HttpWebResponse hs = (HttpWebResponse)hr.GetResponse();//獲取回覆
StreamReader sr = new StreamReader(hs.GetResponseStream(), Encoding.UTF8);//獲取回覆流
XmlTextReader xrd = new XmlTextReader(sr);//用回覆流初始化XML讀寫器
while (xrd.Read() && flag != 0)//按指定邏輯操作xml讀寫器
{
         if (xrd.NodeType == XmlNodeType.Element)
         {
               while (xrd.MoveToNextAttribute())
               {
                       if (xrd.Name == "valid")
                       {
                                valid = Convert.ToBoolean(xrd.Value);
                                ++flag;
                                break;
                        }
                        else if (xrd.Name == "name" && xrd.Value == "aid")
                         {
                                xrd.MoveToNextAttribute();
                                org = xrd.Value;
                                ++flag;
                                break;
                         }
                         else if (xrd.Name == "name" && xrd.Value == "roles")
                         {
                                xrd.MoveToNextAttribute();
                                role = xrd.Name;
                                ++flag;
                                break;
                         }
                  }
          }
}