Session and Cookie of ASP. NET form

Use HttpWebRequest to submit ASP. NET forms and keep Session and Cookie

For various reasons, we sometimes need to capture some information from the Internet, some pages can be opened directly, and some pages can be opened only after login. This document describes a complete example of using HttpWebRequest and HttpWebResponse to automatically submit ASP. NET forms and maintain Session and Cookie. All source code in this article: AutoPostWithCookies.rar

Three pages are involved: MyLogin.aspx,LoginOK.htm, Default. aspx:
1) MyLogin. aspx page
2)LoginOK.htm page
3) Default. aspx page

The following code submits an ASP. NET form to complete automatic logon:

 
 

  
  
Try
  
  
{
  
  
CookieContainercookieContainer=NewCookieContainer();
  
  
 
  
  
//////////////////////////////////////// ///////////
  
  
// 1. Open the MyLogin. aspx page and obtain VeiwState & EventValidation
  
  
//////////////////////////////////////// ///////////
  
  
// Set parameters for opening the page
  
  
StringURI="Http: // localhost: 1165/WebTest/MyLogin. aspx";
  
  
HttpWebRequestrequest= WebRequest. Create (URI) asHttpWebRequest;
  
  
Request. Method="GET";
  
  
Request. KeepAlive=False;
  
  
 
  
  
// Receive the returned page
  
  
HttpWebResponseresponse=Request. GetResponse () asHttpWebResponse;
  
  
System. IO. StreamresponseStream= Response. GetResponseStream ();
  
  
System. IO. StreamReaderreader=NewSystem. IO. StreamReader (responseStream, Encoding. UTF8 );
  
  
StringsrcString=Reader. ReadToEnd ();
  
  
 
  
  
// Obtain the VeiwState of the page
  
  
StringviewStateFlag= "Id = \"_ VIEWSTATE\"Value= \"";
  
  
Inti=SrcString. IndexOf (viewStateFlag) + viewStateFlag. Length;
  
  
Intj=SrcString. IndexOf ("\" ", I );
  
  
StringviewState=SrcString. Substring (I, j-I );
  
  
 
  
  
// Obtain EventValidation of the page
  
  
StringeventValidationFlag= "Id = \"_ EVENTVALIDATION\"Value= \"";
  
  
I=SrcString. IndexOf (eventValidationFlag) + eventValidationFlag. Length;
  
  
J=SrcString. IndexOf ("\" ", I );
  
  
StringeventValidation=SrcString. Substring (I, j-I );
  
  
 
  
  
//////////////////////////////////////// ///////////
  
  
// 2. Automatically fill and submit the MyLogin. aspx page
  
  
//////////////////////////////////////// ///////////
  
  
// Text of the submit button
  
  
StringsubmitButton="Login";
  
  
 
  
  
// User name and password
  
  
StringuserName="1";
  
  
Stringpassword="1";
  
  
 
  
  
// Convert the text into a URL encoded string
  
  
ViewState=System. Web. HttpUtility. UrlEncode (viewState );
  
  
EventValidation=System. Web. HttpUtility. UrlEncode (eventValidation );
  
  
SubmitButton=System. Web. HttpUtility. UrlEncode (submitButton );
  
  
 
  
  
// String data to be submitted. Format: User=Uesr1&Password=123 
  
  
StringformatString=
  
  
"UserName = {0} & password = {1} & loginButton = {2} & __ VIEWSTATE = {3} & __ EVENTVALIDATION = {4 }";
  
  
StringStringpostString=
  
  
String. Format (formatString, userName, password, submitButton, viewState, eventValidation );
  
  
 
  
  
// Convert the submitted string data to a byte array
  
  
Byte []PostData=Encoding. ASCII. GetBytes (postString );
  
  
 
  
  
// Set parameters for submission
  
  
Request=WebRequest. Create (URI) asHttpWebRequest;
  
  
Request. Method="POST";
  
  
Request. KeepAlive=False;
  
  
Request. ContentType="Application/x-www-form-urlencoded";
  
  
Request. CookieContainer=CookieContainer;
  
  
Request. ContentLength=PostData. Length;
  
  
 
  
  
// Submit request data
  
  
System. IO. StreamoutputStream=Request. GetRequestStream ();
  
  
OutputStream. Write (postData, 0, postData. Length );
  
  
OutputStream. Close ();
  
  
 
  
  
// Receive the returned page
  
  
Response=Request. GetResponse () asHttpWebResponse;
  
  
ResponseResponseStream= Response. GetResponseStream ();
  
  
Reader=NewSystem. IO. StreamReader (responseStream, Encoding. GetEncoding ("GB2312 "));
  
  
SrcString=Reader. ReadToEnd ();
  
  
 
  
  
//////////////////////////////////////// ///////////
  
  
// 3. Open the Default. aspx page
  
  
//////////////////////////////////////// ///////////
  
  
// Set parameters for opening the page
  
  
URI="Http: // localhost: 1165/WebTest/Default. aspx";
  
  
Request=WebRequest. Create (URI) asHttpWebRequest;
  
  
Request. Method="GET";
  
  
Request. KeepAlive=False;
  
  
Request. CookieContainer=CookieContainer;
  
  
 
  
  
// Receive the returned page
  
  
Response=Request. GetResponse () asHttpWebResponse;
  
  
ResponseResponseStream= Response. GetResponseStream ();
  
  
Reader=NewSystem. IO. StreamReader (responseStream, Encoding. UTF8 );
  
  
SrcString=Reader. ReadToEnd ();
  
  
 
  
  
//////////////////////////////////////// ///////////
  
  
// 4. Analyze the returned page
  
  
//////////////////////////////////////// ///////////
  
  
//
  
  
}
  
  
Catch (WebExceptionwe)
  
  
{
  
  
Stringmsg=We. Message;
  
  
}
 
 

Note:
1) The Cookie container CookieContainer is used to maintain the Session and Cookie. For details, see the red code section.
2) When you POST an ASP. NET page, you need to POST the VeiwState and EventValidation data together. The above introduces ASP. NET forms and maintains Session and Cookie

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