c# 获取网页中指定的字符串信息的实例代码

       private void button2_click(object sender, eventargs e)
          {
              // create a request for the url.  
              webrequest request = webrequest.create("http://www.baidu.com/");
              // if required by the server, set the credentials.
              request.credentials = credentialcache.defaultcredentials;
              // get the response.
          httpwebresponse response = (httpwebresponse)request.getresponse();
              // display the status.
             messagebox.show(response.statusdescription);
             console.writeline(response.statusdescription);
             // get the stream containing content returned by the server.
             stream datastream = response.getresponsestream();
             // open the stream using a streamreader for easy access.
             streamreader reader = new streamreader(datastream, encoding.default);
             // read the content.
             string responsefromserver = reader.readtoend();
             //截取数据
             int i = responsefromserver.indexof("京");
             string databid = responsefromserver.substring(i, 12);

             // display the content.
             messagebox.show(databid);
             console.writeline(responsefromserver);
             // cleanup the streams and the response.
             reader.close();
             datastream.close();
             response.close();
         }