//先提出一个提交第1页的C#程序

//定义变量
#region
string postString = string.Empty;        //Post字串
string stringResponse = string.Empty;    //接收服务器应答字串
byte[] postData;                         //Post Data
ASCIIEncoding encoding = new ASCIIEncoding();             //代码转换时使用
string cookieheader = string.Empty;                       //Cookies Header
//CookieCollection cookieCollection;                        //创建CookieCollection对象cookieCollection
CookieContainer cookContainer = new CookieContainer();  //创建CookieContainer对象cookieContainer
#endregion

//第1页Login
#region
//初始化变量和POST串
#region
  
#region
string urlstring = "http://192.168.104.35:8001/";
string ViewState = "/wEPDwUKMTEyMTc3MTQwNmRkLjlNkqKUMAkS3auwl+zhtnVIkNg=";
string EventValidation = "/wEWBAL0/ZalCAKG3rm9CgKPndvpBwKC3IeGDN9sVaGWqHIZJdkOjZJcmALtdHsu";
string submitButton = "登录";

submitButton = System.Web.HttpUtility.UrlEncode(submitButton);
viewState = System.Web.HttpUtility.UrlEncode(viewState);
eventValidation = System.Web.HttpUtility.UrlEncode(eventValidation);
#endregion

//要提交表单的URI字符串
#region
string strUsername = this.textUsername.Text;
string strPassword = this.textPassword.Text;

//要提交的字符串数据。格式形如:user=uesr1&password=123
postString = "textUsername=" + strUsername + "&textPassword=" + strPassword;
postString += "&btnLogin=" + submitButton + "&__EVENTVALIDATION=" + eventValidation + "&__VIEWSTATE=" + viewState;

//将字符串转换成字节数组
postData = Encoding.ASCII.GetBytes(postString);
#endregion //要提交表单的URI字符串  //要提交表单的URI字符串
#endregion

//进行POST的准备工作了获取服务器返回信息,并GET Cookies
#region
//初始化HttpWebRequest
#region
//创建HttpWebRequest对象hwResquest
HttpWebRequest hwResquest = (HttpWebRequest)WebRequest.Create(new Uri(uriString));

//准备Web请求,初始化hwResquest
//写入开始后不能设置此项: hwResquest.ContentLength = postData.Length;
hwResquest.ContentLength = postData.Length;
hwResquest.Method = "POST";
hwResquest.CookieContainer = cookContainer;
hwResquest.ContentType = "application/x-www-form-urlencoded";
hwResquest.UserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.2; .NET CLR 1.1.4322; .NET CLR 2.0.50727)";
#endregion

//保存或设置Cookie
#region
if (cookieheader.Equals(string.Empty))
{
cookieheader = hwResquest.CookieContainer.GetCookieHeader(new Uri(uriString));
}
if (!cookieheader.Equals(string.Empty) && cookieheader.Length != 0)
{
hwResquest.CookieContainer.SetCookies(new Uri(uriString), cookieheader);
cookContainer = hwResquest.CookieContainer;
}
#endregion

//向服务器发送POST数据的请求、处理应答、显示服务器应答结果
#region
try
{
//建立请求流、发送Post请求、关闭并释放流,当有Cookies时,获得Cookies
#region
//当在子类中重写时,返回用于将数据写入 Internet 资源的 Stream
System.IO.Stream requestStream = hwResquest.GetRequestStream();

//发送POST请求
requestStream.Write(postData, 0, postData.Length);

//关闭并释放流
requestStream.Close();
//当有Cookies时,获得Cookies
//hwResquest.GetResponse().Close();
//cookieCollection = hwResquest.CookieContainer.GetCookies(new Uri(uriString));
#endregion

//应答处理
#region
//初始化HttpWebResponse对象hwResponse为了获得服务器应答
HttpWebResponse hwResponse = (HttpWebResponse)hwResquest.GetResponse();

//判断是否成功
if (hwResponse.StatusCode == HttpStatusCode.OK)
Console.WriteLine("\nRequest succeeded and the requested information is in the response ,Description : {0}",
hwResponse.StatusDescription);
Uri myUri=new Uri (uriString );
if (myUri.Equals(hwResponse.ResponseUri))
Console.WriteLine("\nThe Request Uri was not redirected by the server");
else
Console.WriteLine("\nThe Request Uri was redirected to :{0}", hwResponse.ResponseUri);

Console.WriteLine("\nThe Uri that responded for the Request is   {0}", hwResquest.RequestUri);


// Release resources of response object.

//获得应答流,并转换为UTF8格式
System.IO.StreamReader responseStream = new StreamReader(hwResponse.GetResponseStream(), Encoding.UTF8);
#endregion

//转换为字符串,显示服务器应答结果到re.Text
#region
stringResponse = responseStream.ReadToEnd();
responseStream.Close();

re.Text = stringResponse;
#endregion
}
catch (WebException we)
{
MessageBox.Show(we.Message);
}
#endregion
#endregion
MessageBox.Show("成功提交第1页");
#endregion

//刚才贴的代码格式没有了，重新贴出来
//定义变量
#region
  string postString = string.Empty;        //Post字串
  string stringResponse = string.Empty;    //接收服务器应答字串
  byte[] postData;                         //Post Data
  ASCIIEncoding encoding = new ASCIIEncoding();             //代码转换时使用
  string cookieheader = string.Empty;                       //Cookies Header
  //CookieCollection cookieCollection;                        //创建CookieCollection对象cookieCollection
  CookieContainer cookContainer = new CookieContainer();  //创建CookieContainer对象cookieContainer
#endregion

//第1页Login
#region
  //初始化变量和POST串
  #region
    
    #region
      string urlstring = "http://192.168.104.35:8001/";
      string ViewState = "/wEPDwUKMTEyMTc3MTQwNmRkLjlNkqKUMAkS3auwl+zhtnVIkNg=";
      string EventValidation = "/wEWBAL0/ZalCAKG3rm9CgKPndvpBwKC3IeGDN9sVaGWqHIZJdkOjZJcmALtdHsu";
      string submitButton = "登录";

      submitButton = System.Web.HttpUtility.UrlEncode(submitButton);
      viewState = System.Web.HttpUtility.UrlEncode(viewState);
      eventValidation = System.Web.HttpUtility.UrlEncode(eventValidation);
    #endregion

    //要提交表单的URI字符串
    #region
      string strUsername = this.textUsername.Text;
      string strPassword = this.textPassword.Text;

      //要提交的字符串数据。格式形如:user=uesr1&password=123
      postString = "textUsername=" + strUsername + "&textPassword=" + strPassword;
      postString += "&btnLogin=" + submitButton + "&__EVENTVALIDATION=" + eventValidation + "&__VIEWSTATE=" + viewState;

      //将字符串转换成字节数组
      postData = Encoding.ASCII.GetBytes(postString);
    #endregion //要提交表单的URI字符串  //要提交表单的URI字符串
  #endregion

  //进行POST的准备工作了获取服务器返回信息,并GET Cookies
  #region
    //初始化HttpWebRequest
    #region
      //创建HttpWebRequest对象hwResquest
      HttpWebRequest hwResquest = (HttpWebRequest)WebRequest.Create(new Uri(uriString));

      //准备Web请求,初始化hwResquest
      //写入开始后不能设置此项: hwResquest.ContentLength = postData.Length;
      hwResquest.ContentLength = postData.Length;
      hwResquest.Method = "POST";
      hwResquest.CookieContainer = cookContainer;
      hwResquest.ContentType = "application/x-www-form-urlencoded";
      hwResquest.UserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.2; .NET CLR 1.1.4322; .NET CLR 2.0.50727)";
    #endregion

    //保存或设置Cookie
    #region
      if (cookieheader.Equals(string.Empty))
      {
        cookieheader = hwResquest.CookieContainer.GetCookieHeader(new Uri(uriString));
      }
      if (!cookieheader.Equals(string.Empty) && cookieheader.Length != 0)
      {
        hwResquest.CookieContainer.SetCookies(new Uri(uriString), cookieheader);
        cookContainer = hwResquest.CookieContainer;
      }
    #endregion

    //向服务器发送POST数据的请求、处理应答、显示服务器应答结果
    #region
      try
      {
        //建立请求流、发送Post请求、关闭并释放流,当有Cookies时,获得Cookies
        #region
          //当在子类中重写时,返回用于将数据写入 Internet 资源的 Stream
          System.IO.Stream requestStream = hwResquest.GetRequestStream();

          //发送POST请求
          requestStream.Write(postData, 0, postData.Length);
          
          //关闭并释放流
          requestStream.Close();
          //当有Cookies时,获得Cookies
          //hwResquest.GetResponse().Close();
          //cookieCollection = hwResquest.CookieContainer.GetCookies(new Uri(uriString));
        #endregion

        //应答处理
        #region
          //初始化HttpWebResponse对象hwResponse为了获得服务器应答
          HttpWebResponse hwResponse = (HttpWebResponse)hwResquest.GetResponse();

          //判断是否成功
          if (hwResponse.StatusCode == HttpStatusCode.OK)
            Console.WriteLine("\nRequest succeeded and the requested information is in the response ,Description : {0}",
                      hwResponse.StatusDescription);
          Uri myUri=new Uri (uriString );
          if (myUri.Equals(hwResponse.ResponseUri))
            Console.WriteLine("\nThe Request Uri was not redirected by the server");
          else
            Console.WriteLine("\nThe Request Uri was redirected to :{0}", hwResponse.ResponseUri);

          Console.WriteLine("\nThe Uri that responded for the Request is   {0}", hwResquest.RequestUri);


          // Release resources of response object.

          //获得应答流,并转换为UTF8格式
          System.IO.StreamReader responseStream = new StreamReader(hwResponse.GetResponseStream(), Encoding.UTF8);
        #endregion

        //转换为字符串,显示服务器应答结果到re.Text
        #region
          stringResponse = responseStream.ReadToEnd();
          responseStream.Close();

          re.Text = stringResponse;
        #endregion
      }
      catch (WebException we)
      {
        MessageBox.Show(we.Message);
      }
    #endregion
  #endregion
  MessageBox.Show("成功提交第1页");
#endregion

好帖子,学习了。

你两个post是独立的，为什么不用WebClient？

用CookieContainer啊。
CookieContainer container;
登录时
request.CookieContainer=container;

post数据时带着container就可以了

//先提出一个提交第1页的C#程序



//定义变量

#region

string postString = string.Empty;        //Post字串

string stringResponse = string.Empty;    //接收服务器应答字串

byte[] postData;                         //Post Data

ASCIIEncoding encoding = new ASCIIEncoding();             //代码转换时使用

string cookieheader = string.Empty;                       //Cookies Header

//CookieCollection cookieCollection;                        //创建CookieCollection对象cookieCollection

CookieContainer cookContainer = new CookieContainer();  //创建CookieContainer对象cookieContainer

#endregion



//第1页Login

#region

//初始化变量和POST串

#region

  

#region

string urlstring = "http://192.168.104.35:8001/";

string ViewState = "/wEPDwUKMTEyMTc3MTQwNmRkLjlNkqKUMAkS3auwl+zhtnVIkNg=";

string EventValidation = "/wEWBAL0/ZalCAKG3rm9CgKPndvpBwKC3IeGDN9sVaGWqHIZJdkOjZJcmALtdHsu";

string submitButton = "登录";



submitButton = System.Web.HttpUtility.UrlEncode(submitButton);

viewState = System.Web.HttpUtility.UrlEncode(viewState);

eventValidation = System.Web.HttpUtility.UrlEncode(eventValidation);

#endregion



//要提交表单的URI字符串

#region

string strUsername = this.textUsername.Text;

string strPassword = this.textPassword.Text;



//要提交的字符串数据。格式形如:user=uesr1&password=123

postString = "textUsername=" + strUsername + "&textPassword=" + strPassword;

postString += "&btnLogin=" + submitButton + "&__EVENTVALIDATION=" + eventValidation + "&__VIEWSTATE=" + viewState;



//将字符串转换成字节数组

postData = Encoding.ASCII.GetBytes(postString);

#endregion //要提交表单的URI字符串  //要提交表单的URI字符串

#endregion



//进行POST的准备工作了获取服务器返回信息,并GET Cookies

#region

//初始化HttpWebRequest

#region

//创建HttpWebRequest对象hwResquest

HttpWebRequest hwResquest = (HttpWebRequest)WebRequest.Create(new Uri(uriString));



//准备Web请求,初始化hwResquest

//写入开始后不能设置此项: hwResquest.ContentLength = postData.Length;

hwResquest.ContentLength = postData.Length;

hwResquest.Method = "POST";

hwResquest.CookieContainer = cookContainer;

hwResquest.ContentType = "application/x-www-form-urlencoded";

hwResquest.UserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.2; .NET CLR 1.1.4322; .NET CLR 2.0.50727)";

#endregion



//保存或设置Cookie

#region

if (cookieheader.Equals(string.Empty))

{

cookieheader = hwResquest.CookieContainer.GetCookieHeader(new Uri(uriString));

}

if (!cookieheader.Equals(string.Empty) && cookieheader.Length != 0)

{

hwResquest.CookieContainer.SetCookies(new Uri(uriString), cookieheader);

cookContainer = hwResquest.CookieContainer;

}

#endregion



//向服务器发送POST数据的请求、处理应答、显示服务器应答结果

#region

try

{

//建立请求流、发送Post请求、关闭并释放流,当有Cookies时,获得Cookies

#region

//当在子类中重写时,返回用于将数据写入 Internet 资源的 Stream

System.IO.Stream requestStream = hwResquest.GetRequestStream();



//发送POST请求

requestStream.Write(postData, 0, postData.Length);



//关闭并释放流

requestStream.Close();

//当有Cookies时,获得Cookies

//hwResquest.GetResponse().Close();

//cookieCollection = hwResquest.CookieContainer.GetCookies(new Uri(uriString));

#endregion



//应答处理

#region

//初始化HttpWebResponse对象hwResponse为了获得服务器应答

HttpWebResponse hwResponse = (HttpWebResponse)hwResquest.GetResponse();



//判断是否成功

if (hwResponse.StatusCode == HttpStatusCode.OK)

Console.WriteLine("\nRequest succeeded and the requested information is in the response ,Description : {0}",

hwResponse.StatusDescription);

Uri myUri=new Uri (uriString );

if (myUri.Equals(hwResponse.ResponseUri))

Console.WriteLine("\nThe Request Uri was not redirected by the server");

else

Console.WriteLine("\nThe Request Uri was redirected to :{0}", hwResponse.ResponseUri);



Console.WriteLine("\nThe Uri that responded for the Request is   {0}", hwResquest.RequestUri);





// Release resources of response object.



//获得应答流,并转换为UTF8格式

System.IO.StreamReader responseStream = new StreamReader(hwResponse.GetResponseStream(), Encoding.UTF8);

#endregion



//转换为字符串,显示服务器应答结果到re.Text

#region

stringResponse = responseStream.ReadToEnd();

responseStream.Close();



re.Text = stringResponse;

#endregion

}

catch (WebException we)

{

MessageBox.Show(we.Message);

}

#endregion

#endregion

MessageBox.Show("成功提交第1页");

#endregion

发的时候把代码放在[ code ] [ /code]这个标记中间就有格式了

第2页在第1页提交成功以后再提交第2页，
第1页提交的目的是要取到SESSIONID
//初始化HttpWebResponse对象hwResponse为了获得服务器应答
HttpWebResponse hwResponse = (HttpWebResponse)hwResquest.GetResponse();
在这之后要找到服务器的SESSIONID，类似下面的方法。
            hwResponse.Cookies["SessionID"]//不同的服务器存SessionID的Cookie名称不一样，可以使用HttpWatch或浏览器的开发者工具追踪一下，很容易就可以知道。
存下来后在第2个页提交的时候要把这个作为Cookie的内容之一一起提交，否则服务器还是认为你没有登录。

hwResquest.ContentLength = postData.Length;
hwResquest.Method = "POST";
hwResquest.CookieContainer = cookContainer;
有些不明白的，到这里 cookContainer还是空值吧

if (cookieheader.Equals(string.Empty)){cookieheader = hwResquest.CookieContainer.GetCookieHeader(new Uri(uriString));}

if (!cookieheader.Equals(string.Empty) && cookieheader.Length != 0){hwResquest.CookieContainer.SetCookies(new Uri(uriString), cookieheader);cookContainer = hwResquest.CookieContainer;}

到这里cookContainer有值吗，如果有post请求是否完成，菜鸟看不懂，这样是带着cookies post吗