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

从网上找到了Jake LinJake'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;
}

 

posted @ 2010-08-31 11:55  westfruit  阅读(1275)  评论(0编辑  收藏  举报