.NET 网站自动登录

首先，我们先定义一些变量：
C# code

private const string NET_SESSIONID= "ASP.NET_SessionId=";
private const string CLIENTKEY = "ClientKey=";
string aspcookie = "";
private string html = "";
private string sessionId = "";
private string clientKey = "";
private string viewState = "";

一、利用HttpWebRequest获取CSDN的登录信息，如ASP.NET_SessionId、ClientKey、__VIEWSTATE。这步可以放在Login_Load中，下面是代码：
C# code

private void Login_Load(object sender, EventArgs e)
{
    HttpWebRequest request = WebRequest.Create("http://passport.csdn.net/UserLogin.aspx") as HttpWebRequest;
    request.Credentials = CredentialCache.DefaultCredentials;
    request.Accept = "*/*";
    request.Referer = "http://passport.csdn.net/UserLogin.aspx";
    request.UserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; .NET4.0C; .NET4.0E)";
    request.Method = "GET";
    request.KeepAlive = true;
    request.Headers.Set("Accept-Language", "zh-CN");
    request.Headers.Set("Accept-Encoding", "gzip, deflate");

    HttpWebResponse response = request.GetResponse() as HttpWebResponse;
    System.IO.Stream responseStream = response.GetResponseStream();
    System.IO.StreamReader reader = new System.IO.StreamReader(responseStream, Encoding.GetEncoding("utf-8"));
    html = reader.ReadToEnd();

    string viewStateFlag = "id=\"__VIEWSTATE\" value=\"";
    int i = html.IndexOf(viewStateFlag) + viewStateFlag.Length;
    int j = html.IndexOf("\"", i);
    viewState = html.Substring(i, j - i);

    aspcookie = response.Headers.Get("Set-Cookie");
    sessionId = GetSessionId();
    clientKey = GetClientKey();
    // 获取图片验证码
    GetCode();
}
 /// <summary>
/// 获取ClientKey
/// </summary>
/// <returns></returns>
private string GetClientKey()
{
    // 这个仅仅是用来获取ClientKey值的长度
 string id = "bb32434c-3bb3-4e44-92c3-8952f631ca87";
    int index = aspcookie.IndexOf(CLIENTKEY) + CLIENTKEY.Length;
    String str = aspcookie.Substring(index, id.Length);
    return str;
}
/// <summary>
/// 获取ASP.NET_SessionId=
/// </summary>
/// <returns></returns>
private string GetSessionId()
{
    string id = "5mhl0tvbw5shlpnhxgwnck45";
    int index = aspcookie.IndexOf(NET_SESSIONID) + NET_SESSIONID.Length;
    String str = aspcookie.Substring(index, id.Length);
    return str;
}

二、获取图片验证码，在这一步中需要注意的是，因为我们用的是另外一个HttpWebRequest去获取，所以为了保持获取的验证码与登录页面的Session一致，我们需要把Session等信息放入Header中去，下面是代码：
C# code

/// <summary>
/// 产生新的验证码
/// </summary>
private void GetCode()
{
    try
    {
    CookieCollection cookies = new CookieCollection();
    cookies.Add(new Cookie("ASP.NET_SessionId",sessionId));
    cookies.Add(new Cookie("ClientKey",clientKey));

    HttpWebRequest httpWebRequest;
    HttpWebResponse webResponse;
    byte[] byteRequest = { };
    httpWebRequest = (HttpWebRequest)HttpWebRequest.Create("http://passport.csdn.net/ShowExPwd.aspx");
    CookieContainer co = new CookieContainer();
    co.Add(new Uri("http://passport.csdn.net"), cookies);
    httpWebRequest.CookieContainer = co;
    httpWebRequest.Accept = "*/*";
    httpWebRequest.Referer = "http://passport.csdn.net/UserLogin.aspx";
    httpWebRequest.UserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; .NET4.0C; .NET4.0E)";
    httpWebRequest.Method = "GET";
    httpWebRequest.Headers.Set("Accept-Encoding", "gzip, deflate");
    httpWebRequest.Headers.Set("Accept-Language", "zh-CN");
    httpWebRequest.KeepAlive = true;

    webResponse = (HttpWebResponse)httpWebRequest.GetResponse();
    Stream responseStream = webResponse.GetResponseStream();
    Image original = Image.FromStream(responseStream);
    Bitmap bitMap = new Bitmap(original);
    this.pictureBox1.Image = bitMap;
    responseStream.Close();
    }
    catch (Exception exception)
    {
    MessageBox.Show("ERROR:" + exception.Message);
    }
}

三、最后一步是登录事件，登录很简单，把相关的信息放入请求数据中就行了。
C# code

private void btnLogin_Click(object sender, EventArgs e)
{
    HttpWebRequest httpWebRequest;
    HttpWebResponse webResponse;

    string randnum = txtRandnum.Text;
    string password = txtPassword.Text;
    string loginname = txtUserName.Text;

    string postData = "ctl00$CPH_Content$tb_LoginNameOrLoginEmail={0}&ctl00$CPH_Content$tb_Password={1}&ctl00$CPH_Content$tb_ExPwd={2}&__EVENTTARGET=&__EVENTARGUMENT=&__VIEWSTATE={3}&ClientKey={4}&from={5}&MailParameters=&PrePage=&ctl00$CPH_Content$Image_Login.x=46&ctl00$CPH_Content$Image_Login.y=9";
    postData = string.Format(postData, System.Web.HttpUtility.UrlEncode(loginname),System.Web.HttpUtility.UrlEncode(password),System.Web.HttpUtility.UrlEncode(randnum), System.Web.HttpUtility.UrlEncode(viewState), clientKey, System.Web.HttpUtility.UrlEncode("http://hi.csdn.net/"));
    byte[] byteRequest = Encoding.UTF8.GetBytes(postData);

    CookieCollection cookies = new CookieCollection();
    cookies.Add(new Cookie("ASP.NET_SessionId", sessionId));
    cookies.Add(new Cookie("ClientKey", clientKey));
    cookies.Add(new Cookie("UN",loginname));

    httpWebRequest = (HttpWebRequest)HttpWebRequest.Create("http://passport.csdn.net/UserLogin.aspx");
    CookieContainer co = new CookieContainer();
    co.Add(new Uri("http://passport.csdn.net"), cookies);
    httpWebRequest.CookieContainer = co;
    httpWebRequest.ContentType = "application/x-www-form-urlencoded";
    httpWebRequest.Accept = "image/jpeg, application/x-ms-application, image/gif, application/xaml+xml, image/pjpeg, application/x-ms-xbap, application/x-shockwave-flash, */*";
    httpWebRequest.Referer = "http://passport.csdn.net/UserLogin.aspx";
    httpWebRequest.UserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; .NET4.0C; .NET4.0E)";
    httpWebRequest.Method = "POST";
    httpWebRequest.KeepAlive = true;
    httpWebRequest.Headers.Set("Cache-Control", "no-cache");
    httpWebRequest.Headers.Set("Accept-Encoding", "gzip, deflate");
    httpWebRequest.Headers.Set("Accept-Language", "zh-CN");

    httpWebRequest.ContentLength = byteRequest.Length;
    Stream stream;
    stream = httpWebRequest.GetRequestStream();
    stream.Write(byteRequest, 0, byteRequest.Length);
    stream.Close();
    webResponse = (HttpWebResponse)httpWebRequest.GetResponse();
    System.IO.Stream responseStream = webResponse.GetResponseStream();

    String header = webResponse.Headers.ToString();
    Stream getStream = webResponse.GetResponseStream();
    long contentLength = webResponse.ContentLength;

    byte[] outBytes = new byte[contentLength];
    outBytes = ReadFully(getStream);
    getStream.Close();

    getStream = new MemoryStream(outBytes);
    StreamReader streamReader = new StreamReader(getStream, Encoding.UTF8);
    string getString = streamReader.ReadToEnd();
    streamReader.Close();
    getStream.Close();

}

static byte[] ReadFully(Stream stream)
{
    byte[] buffer = new byte[128];
    using (MemoryStream ms = new MemoryStream())
    {
    while (true)
    {
        int read = stream.Read(buffer, 0, buffer.Length);
        if (read <= 0)
        return ms.ToArray();
        ms.Write(buffer, 0, read);
    }
    }
}

其中，在如果把数据以及需要把哪些数据Post到服务器中花费了不少时间，后来利用HttpAnalyzer来抓取浏览器中登录的数据包与WinForm登录的数据包进行了对比，才找出问题所在。

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