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
///////////////////////////////////////////////////
//