string InfoUrl = "http://cn.bing.com/HPImageArchive.aspx?idx=0&n=1";HttpWebRequest request = (HttpWebRequest)WebRequest.Create(InfoUrl);request.Method = "GET"; request.ContentType = "text/html;charset=UTF-8";string XmlString;using (HttpWebResponse response = (HttpWebResponse)request.GetResponse()){  Stream myResponseStream = response.GetResponseStream();  using (StreamReader myStreamReader = new StreamReader(myResponseStream, Encoding.UTF8))  {    XmlString = myStreamReader.ReadToEnd();  }}// 定義正則表達式用來匹配標簽Regex regImg = new Regex("<Url>(?<imgUrl>.*?)</Url>", RegexOptions.IgnoreCase);// 搜索匹配的字符串MatchCollection matches = regImg.Matches(XmlString);// 取得匹配項列表string ImageUrl = "http://www.bing.com" + matches[0].Groups["imgUrl"].Value;background_image.Src = ImageUrl;