C#的HttpWebRequest编程，支持带ViewState的网页POST请求

最新推荐文章于 2016-01-14 14:35:13 发布

weixin_34277853

最新推荐文章于 2016-01-14 14:35:13 发布

阅读量123

点赞数

本文详细介绍了如何使用.NET Compact Framework通过GET请求获取网页内容，解析出关键信息如ViewState和EventValidation，进而构造POST请求数据包，最终实现模拟网页POST提交的效果，并成功提取了特定网页的数据。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

从网上找到了Jake Lin（Jake's Blog on 博客园）的一篇文章《.NET Compact Framework下HttpWebRequest开发》，在他的代码基础上稍加修改，可以编程模拟网页POST提交的效果。

在主程序上用了个循环，再将取出的网页用正则表达式把想要的信息取出来，最后成功地提取出了石油大学附中2010小升初的成绩表。

static private string SearchURL( string id)
{
try
{
// Get the ViewState and EventValidation
  HttpWebRequest request = WebRequest.Create(URI) as HttpWebRequest;
  request.Method = " GET " ;
  request.KeepAlive = false ;

  // Get the response
  HttpWebResponse response = request.GetResponse() as HttpWebResponse;
  System.IO.Stream responseStream = response.GetResponseStream();
  System.IO.StreamReader reader = new System.IO.StreamReader(responseStream, Encoding.UTF8);
  string srcString = reader.ReadToEnd();

  // Get the ViewState
  string viewStateFlag = " id=\ " __VIEWSTATE\ " value=\ "" ;
  int i = srcString.IndexOf(viewStateFlag) + viewStateFlag.Length;
  int j = srcString.IndexOf( " \ "" , i);
  string viewState = srcString.Substring(i, j - i);

  // Get the ViewState
  string EventValidationFlag = " id=\ " __EVENTVALIDATION\ " value=\ "" ;
  i = srcString.IndexOf(EventValidationFlag) + EventValidationFlag.Length;
  j = srcString.IndexOf( " \ "" , i);
  string eventValidation = srcString.Substring(i, j - i);

  // Compose the URL
  viewState = Uri.EscapeDataString(viewState);
  eventValidation = Uri.EscapeDataString(eventValidation);
  string strSearch = Uri.EscapeDataString( " 查询 " );

  string formatString = " __VIEWSTATE={0}&__EVENTVALIDATION={1}&TextBox1={2}&Button1={3} " ;
  string postString = string .Format(formatString, viewState, eventValidation, id,strSearch);

  // Change to byte[]
  byte [] postData = Encoding.ASCII.GetBytes(postString);

  // Compose the new request
  request = WebRequest.Create(URI) as HttpWebRequest;
  request.Method = " POST " ;
  request.KeepAlive = false ;
  request.ContentType = " application/x-www-form-urlencoded " ;
  request.ContentLength = postData.Length;

  System.IO.Stream outputStream = request.GetRequestStream();
  outputStream.Write(postData, 0 , postData.Length);
  outputStream.Close();

  // Get the new response
  response = request.GetResponse() as HttpWebResponse;
  responseStream = response.GetResponseStream();
  reader = new System.IO.StreamReader(responseStream);
  srcString = reader.ReadToEnd();
  return srcString;
}
catch (WebException we)
{
  Console.WriteLine( " Communication error, " + we.Message + " please check your connectivity and try again. " , " Error " );
}
catch
{
  Console.WriteLine( " Unknow error. " , " Error " );
}
return null ;
}