[asp.net]利用HttpRequest登录到某个网站，然后获取网站信息

问题：有的网站的相关内容必须要在登录后才可以查看，其登录信息保存在session变量之中。这样，使用asphttp等组件就难以正确得到所要的信息。

解决：使用asp.net中的httprequest和httpresponse来实现。

要点：
1。 通过附加一个cookiecontainer到httprequest对象中，可以得到登录后返回的代表SESSION ID的COOKIE。 见Login方法
2。 将此COOKIE包含在一个cookiecontainer中并附加到另一个HTTPREQUEST请求中，则可以实现SESSION的还原。见getPage方法

源程序如下：
getHttpInfo.aspx:

<% @ Page language="c#" Codebehind="getHttpInfo.aspx.cs" AutoEventWireup="false" Inherits="PdfTest.getHttpInfo"  %>
<! DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"  >
< HTML >
     < HEAD >
         < title > WebForm1 </ title >
         < meta  content ="Microsoft Visual Studio 7.0"  name ="GENERATOR" >
         < meta  content ="C#"  name ="CODE_LANGUAGE" >
         < meta  content ="JavaScript"  name ="vs_defaultClientScript" >
         < meta  content ="http://schemas.microsoft.com/intellisense/ie5"  name ="vs_targetSchema" >
     </ HEAD >
     < body >
         < form  id ="Form1"  method ="post"  runat ="server" >
         </ form >
     </ body >
</ HTML >

getHttpInfo.aspx.cs:

using  System;
using  System.Collections;
using  System.ComponentModel;
using  System.Data;
// using System.Data.OleDb;
using  System.Drawing;
using  System.Web;
using  System.Web.SessionState;
using  System.Web.UI;
using  System.Web.UI.WebControls;
using  System.Web.UI.HtmlControls;
using  System.Net;
using  System.IO;
using  System.Text;
using  System.Text.RegularExpressions;
using  Microsoft.Data.Odbc;

namespace  PdfTest
{
    /**//// <summary>
    /// Summary description for WebForm1.
    /// </summary>
    public class getHttpInfo : System.Web.UI.Page
    {
        protected static string cookieheader;

    
        private void Page_Load(object sender, System.EventArgs e)
        {
            // Put user code to initialize the page here

            string strResult;

            if (HttpContext.Current.Application["cookieheader"] != null)
            {
                cookieheader = (string)HttpContext.Current.Application["cookieheader"];
            }
            else
            {
                //Login into the website and keep the cookie for the session in the application variable
                string strLogin = Login("http://www.thesiteyouwanttovisit/theloginpage.asp", "Action=&USERID=&Password=") ;
            }
            

            strResult = getPage("http://www.thesiteyouwanttovisit/theloginpage.asp", "Action=&data=") ;


            //Write the result to htm file
            FileStream htmFile = new FileStream("c:save.htm", FileMode.OpenOrCreate);
            StreamWriter sw = new StreamWriter(htmFile);
            sw.Write(strResult);
            sw.Close();
            htmFile.Close();

            // output the result
            Response.Write(strResult);
        }


        public static string Login(String url, String paramList) 
        {
            HttpWebResponse res = null;
            string strResult="";

            try 
            {

                HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);
                req.Method = "POST";
                req.ContentType = "application/x-www-form-urlencoded";
                req.AllowAutoRedirect = false;
                CookieContainer cookieCon = new CookieContainer();
                req.CookieContainer = cookieCon;

                StringBuilder UrlEncoded = new StringBuilder();
                Char[] reserved = {'?', '=', '&'};
                byte[] SomeBytes = null;

                if (paramList != null) 
                {
                    int i=0, j;
                    while(i<paramList.Length)
                    {
                        j=paramList.IndexOfAny(reserved, i);
                        if (j==-1)
                        {
                            UrlEncoded.Append(HttpUtility.UrlEncode(paramList.Substring(i, paramList.Length-i)));
                            break;
                        }
                        UrlEncoded.Append(HttpUtility.UrlEncode(paramList.Substring(i, j-i)));
                        UrlEncoded.Append(paramList.Substring(j,1));
                        i = j+1;
                    }
                    SomeBytes = Encoding.UTF8.GetBytes(UrlEncoded.ToString());
                    req.ContentLength = SomeBytes.Length;
                    Stream newStream = req.GetRequestStream();
                    newStream.Write(SomeBytes, 0, SomeBytes.Length);
                    newStream.Close();
                } 
                else 
                {
                    req.ContentLength = 0;
                }


                res = (HttpWebResponse)req.GetResponse();
                cookieheader = req.CookieContainer.GetCookieHeader(new Uri(url));
                HttpContext.Current.Application.Lock();
                HttpContext.Current.Application["cookieheader"] = cookieheader;
                HttpContext.Current.Application.UnLock();

                Stream ReceiveStream = res.GetResponseStream();
                Encoding encode = System.Text.Encoding.GetEncoding("utf-8");
                StreamReader sr = new StreamReader( ReceiveStream, encode );
                Char[] read = new Char[256];
                int count = sr.Read( read, 0, 256 );
                while (count > 0) 
                {
                    String str = new String(read, 0, count);
                    strResult += str;
                    count = sr.Read(read, 0, 256);
                }
            } 
            catch(Exception e) 
            {
                strResult = e.ToString();
            } 
            finally 
            {
                if ( res != null ) 
                {
                    res.Close();
                }
            }

            return strResult;
        }


        public static string getPage(String url, String paramList) 
        {
            HttpWebResponse res = null;
            string strResult = "";

            try 
            {

                HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);
                req.Method = "POST";
                req.KeepAlive = true;
                req.ContentType = "application/x-www-form-urlencoded";
                CookieContainer cookieCon = new CookieContainer();
                req.CookieContainer = cookieCon;
                req.CookieContainer.SetCookies(new Uri(url),cookieheader);
                StringBuilder UrlEncoded = new StringBuilder();
                Char[] reserved = {'?', '=', '&'};
                byte[] SomeBytes = null;

                if (paramList != null) 
                {
                    int i=0, j;
                    while(i<paramList.Length)
                    {
                        j=paramList.IndexOfAny(reserved, i);
                        if (j==-1)
                        {
                            UrlEncoded.Append(HttpUtility.UrlEncode(paramList.Substring(i, paramList.Length-i)));
                            break;
                        }
                        UrlEncoded.Append(HttpUtility.UrlEncode(paramList.Substring(i, j-i)));
                        UrlEncoded.Append(paramList.Substring(j,1));
                        i = j+1;
                    }
                    SomeBytes = Encoding.UTF8.GetBytes(UrlEncoded.ToString());
                    req.ContentLength = SomeBytes.Length;
                    Stream newStream = req.GetRequestStream();
                    newStream.Write(SomeBytes, 0, SomeBytes.Length);
                    newStream.Close();
                } 
                else 
                {
                    req.ContentLength = 0;
                }


                res = (HttpWebResponse)req.GetResponse();
                Stream ReceiveStream = res.GetResponseStream();
                Encoding encode = System.Text.Encoding.GetEncoding("utf-8");
                StreamReader sr = new StreamReader( ReceiveStream, encode );
                Char[] read = new Char[256];
                int count = sr.Read( read, 0, 256 );
                while (count > 0) 
                {
                    String str = new String(read, 0, count);
                    strResult += str;
                    count = sr.Read(read, 0, 256);
                }
            } 
            catch(Exception e) 
            {
                strResult = e.ToString();
            } 
            finally 
            {
                if ( res != null ) 
                {
                    res.Close();
                }
            }

            return strResult;
        }


        Web Form Designer generated code#region Web Form Designer generated code
        override protected void OnInit(EventArgs e)
        {
            //
            // CODEGEN: This call is required by the ASP.NET Web Form Designer.
            //
            InitializeComponent();
            base.OnInit(e);
        }
        
        /**//// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {    
            this.Load += new System.EventHandler(this.Page_Load);

        }
        #endregion

        


    }
}