Jerry Dennany's Occasional Clue

using System;
using System.Text;
using System.Text.RegularExpressions;
using System.Net;
using System.IO;

namespace Dennany.WebScrape {
  class MainClass {
   
    [STAThread]
    static void Main(string[] args) {

      try {
       // Modify as appropriate:
       const string baseUri = "http://remotewebhost/webpagedirectory/";
       const string loginDlgUri = baseUri + "LoginDlg.aspx";
       const string mainConsoleUri = baseUri + "Mainpage.aspx";
       const string username = "myuser";
       const string password = "p@ssw0rd";

       // This cookie container will persist the ASP.NET session ID cookie
       CookieContainer cookies = new CookieContainer();

      // perform the first http request against
      // the asp.net application login dialog.
      HttpWebRequest request =
        (HttpWebRequest) WebRequest.Create(loginDlgUri);

      //get the response object, so that we may get the session cookie.
      HttpWebResponse response =
       (HttpWebResponse)request.GetResponse();
    
      // populate the cookie container.
      request.CookieContainer = cookies;
      response.Cookies =
        request.CookieContainer.GetCookies(request.RequestUri);

      // read the incoming stream containing the login dialog page.
      StreamReader reader =
        new StreamReader(response.GetResponseStream());

      string loginDlgPage = reader.ReadToEnd();

      reader.Close();

      // extract the viewstate value from the login dialog page.
      // We need to post this back,
      // along with the username and password
      string viewState = GetViewState(loginDlgPage);

      // build postback string
      // This string will vary depending on the page. The best
      // way to find out what your postback should look like is to
      // monitor a normal login using a utility like TCPTrace.
      string postback = 
        String.Format("__VIEWSTATE={0}&txtUserName={1}" +
         "&txtPassword={2}&txtMessage=&btnOK=OK",
         viewState, username, password);

      // our second request is the POST of the username / password data.
      HttpWebRequest request2 =
       (HttpWebRequest)WebRequest.Create(loginDlgUri);

      request2.Method = "POST";
      request2.ContentType = "application/x-www-form-urlencoded";
      request2.CookieContainer = cookies;

     // write our postback data into the request stream
     StreamWriter writer =
       new StreamWriter(request2.GetRequestStream());
     writer.Write(postback);
     writer.Close();

     request2.GetResponse().Close();

     // our third request is for the actual webpage after the login.
     HttpWebRequest request3 =
      (HttpWebRequest)WebRequest.Create(mainConsoleUri);
     request3.CookieContainer = cookies;

     reader =
       new StreamReader(request3.GetResponse().GetResponseStream());

     // and read the response
     string page = reader.ReadToEnd();

     reader.Close();

    // our webpage data is in the 'page' string.
    Console.WriteLine(page);
  }

  catch(Exception ex) {
    Console.WriteLine(ex);
  }
 }

  // extract the viewstate data from a page.
  private static string GetViewState(string aspxPage) {
    Regex regex =
     new Regex("(?<=(__viewstate\".value.\")).*(?=\"./>)",RegexOptions.IgnoreCase);

    Match match =
      regex.Match(aspxPage);