asp.net 程序自动提交登陆表单并保持Session及Cookie

代码要点：

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。

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。

部分主要代码：

        CookieContainer cookieContainer = new CookieContainer();

        ///////////////////////////////////////////////////
        // 1. 打开 Login.aspx 页面，获得 VeiwState & EventValidation。
        //如果是登陆页为asp.net页面,需要获取VeiwState及EventValidation
        ///////////////////////////////////////////////////                
        // 设置打开页面的参数
        string URI = http://localhost/Test/Login.aspx;
         HttpWebRequest request = WebRequest.Create(URI) as HttpWebRequest;
         request.Method = "GET";
         request.KeepAlive = false;

        // 接收返回的页面
         HttpWebResponse response = request.GetResponse() as HttpWebResponse;
         System.IO.Stream responseStream = response.GetResponseStream();
         System.IO.StreamReader reader = new System.IO.StreamReader(responseStream,Encoding.UTF8);
        string srcString = reader.ReadToEnd();

        // 获取页面的 VeiwState                
        string viewStateFlag = "id=\"__VIEWSTATE\" value=\"";
        int i = srcString.IndexOf(viewStateFlag) + viewStateFlag.Length;
        int j = srcString.IndexOf("\"", i);
        string viewState = srcString.Substring(i, j - i);

        // 获取页面的 EventValidation                
        string eventValidationFlag = "id=\"__EVENTVALIDATION\" value=\"";
         i = srcString.IndexOf(eventValidationFlag) + eventValidationFlag.Length;
         j = srcString.IndexOf("\"", i);
        string eventValidation = srcString.Substring(i, j - i);

        ///////////////////////////////////////////////////
        // 2. 自动填充并提交 Login.aspx 页面
        ///////////////////////////////////////////////////
        // 提交按钮的文本
        string submitButton = "登录";

        // 用户名和密码
        string userName = "1";
        string password = "1";

        // 将文本转换成 URL 编码字符串
         viewState = System.Web.HttpUtility.UrlEncode(viewState);
         eventValidation = System.Web.HttpUtility.UrlEncode(eventValidation);
         submitButton = System.Web.HttpUtility.UrlEncode(submitButton);

        // 要提交的字符串数据。格式形如:user=uesr1&password=123
        string formatString =
                 "userName={0}&password={1}&loginButton={2}&__VIEWSTATE={3}&__EVENTVALIDATION={4}";
        string postString =
                 string.Format(formatString, userName, password, submitButton, viewState, eventValidation);

        // 将提交的字符串数据转换成字节数组
        byte[] postData = Encoding.ASCII.GetBytes(postString);

        // 设置提交的相关参数
         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
         response = request.GetResponse() as HttpWebResponse;
         responseStream = response.GetResponseStream();
         reader = new System.IO.StreamReader(responseStream,Encoding.GetEncoding("GB2312"));
         srcString = reader.ReadToEnd();

        ///////////////////////////////////////////////////
        // 3. 打开 Default.aspx 页面
        ///////////////////////////////////////////////////
        // 设置打开页面的参数
         URI = "http://localhost:1165/WebTest/Default.aspx";
         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.UTF8);
         srcString = reader.ReadToEnd();

        ///////////////////////////////////////////////////
        // 4. 分析返回的页面
        ///////////////////////////////////////////////////
        //