登录到某个网站并获取网站信息

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、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 desrciption for WebForm1. 
    ///  
    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) { 
                        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){ 
                    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; 
        } 
         
         
        #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); 
        } 
         
        ///  
        /// Required method for Designer support - do not modify 
        /// the contents of this method with the code editor. 
        ///  
        private void InitializeComponent() 
        {  
            this.Load += new System.EventHandler(this.Page_Load); 
        } 
        #endregion 
    } 
}