首先说明：代码片段是从网络获取，然后自己修改。我想好的东西应该拿来分享。
实现原理：当我们采集页面的时候，如果被采集的网站需要登录才能采集。不管是基于Cookie还是基于Session，我们都会首先发送一个Http请求头，这个Http请求头里面就包含了网站需要的Cookie信息。当网站接收到发送过来的Http请求头时，会从Http请求头获取相关的Cookie或者Session信息，然后由程序来处理，决定你是否有权限访问当前页面。
好了，原理搞清楚了，就好办了。我们所要做的仅仅是在采集的时候（或者说HttpWebRequest提交数据的时候），将Cookie信息放入Http请求头里面就可以了。
在这里我提供2种方法。
第一种，直接将Cookie信息放入HttpWebRequest的CookieContainer里。看代码：
protected void Page_Load(object sender, EventArgs e)
{
//设置Cookie，存入Hashtable
Hashtable ht = new Hashtable();
ht.Add("username", "youraccount");
ht.Add("id", "yourid");
this.Collect(ht);
}
public void Collect(Hashtable ht)
{
string content = string.Empty;
string url = "http://www.ibest100.com/需要登录后才能采集的页面";
string host = "http://www.ibest100.com";
try
{
//获取提交的字节
byte[] bs = Encoding.UTF8.GetBytes(content);
//设置提交的相关参数
HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(url);
req.Method = "POST";
req.ContentType = "application/json;charset=utf-8";
req.ContentLength = bs.Length;
//将Cookie放入CookieContainer，然后再将CookieContainer添加到HttpWebRequest
CookieContainer cc = new CookieContainer();
cc.Add(new Uri(host), new Cookie("username", ht["username"].ToString()));
cc.Add(new Uri(host), new Cookie("id", ht["id"].ToString()));
req.CookieContainer = cc;
//提交请求数据
Stream reqStream = req.GetRequestStream();
reqStream.Write(bs, 0, bs.Length);
reqStream.Close();
//接收返回的页面，必须的，不能省略
WebResponse wr = req.GetResponse();
System.IO.Stream respStream = wr.GetResponseStream();
System.IO.StreamReader reader = new System.IO.StreamReader(respStream, System.Text.Encoding.GetEncoding("utf-8"));
string t = reader.ReadToEnd();
System.Web.HttpContext.Current.Response.Write(t);
wr.Close();
}
catch (Exception ex)
{
System.Web.HttpContext.Current.Response.Write("异常在getPostRespone:" + ex.Source + ":" + ex.Message);
}
}
第二种，每次打开采集程序时，需要先到被采集的网站模拟登录一次，获取CookieContainer，然后再采集。看代码：
protected void Page_Load(object sender, EventArgs e)
{
try
{
CookieContainer cookieContainer = new CookieContainer();
string formatString = "username={0}&password={1}";//***************
string postString = string.Format(formatString, "youradminaccount", "yourpassword");
//将提交的字符串数据转换成字节数组
byte[] postData = Encoding.UTF8.GetBytes(postString);
//设置提交的相关参数
string URI = "http://www.ibest100.com/登录页面";//***************
HttpWebRequest request = WebRequest.Create(URI) as HttpWebRequest;
request.Method = "POST";
request.KeepAlive = false;
request.ContentType = "application/x-www-form-urlencoded";
request.CookieContainer = cookieContainer;
request.ContentLength = postData.Length;
// 提交请求数据
System.IO.Stream outputStream = request.GetRequestStream();
outputStream.Write(postData, 0, postData.Length);
outputStream.Close();
//接收返回的页面，必须的，不能省略
HttpWebResponse response = request.GetResponse() as HttpWebResponse;
System.IO.Stream responseStream = response.GetResponseStream();
System.IO.StreamReader reader = new System.IO.StreamReader(responseStream, Encoding.GetEncoding("gb2312"));
string srcString = reader.ReadToEnd();
//打开您要访问的页面
URI = "http://www.ibest100.com/需要登录后才能采集的页面";//***************
request = WebRequest.Create(URI) as HttpWebRequest;
request.Method = "GET";
request.KeepAlive = false;
request.CookieContainer = cookieContainer;
// 接收返回的页面
response = request.GetResponse() as HttpWebResponse;
responseStream = response.GetResponseStream();
reader = new System.IO.StreamReader(responseStream, Encoding.GetEncoding("gb2312"));
srcString = reader.ReadToEnd();
//输出获取的页面或者处理
Response.Write(srcString);
}
catch (WebException we)
{
string msg = we.Message;
Response.Write(msg);
}
}
也许有人会问，如果对方登录的时候要验证码怎么办？那你就用第一种方式吧，只不过需要你分析对方的Cookie。
应用范围：采集数据、论坛发帖、博客发文。
