先来看一看正常的浏览器登录报文情况：

HTTP/1.1 200 OK
Server: Tengine/1.5.2
Date: Sun, 22 Dec 2013 13:39:38 GMT
Content-Type: application/json; charset=utf-8
Connection: keep-alive
Set-Cookie: passToken=Aq3FBlXT880Y+FyC7LB8rYE0wz8nThC2b740zWzDAUt1YZxxxxeZN2NGEYyOKnShUJfZg7dd7LB/wTuijbC8EjM39u77R0pwRfctT3Ch0C/k51gz9F3fMC3NiKQiJvtfpddKcCltHsZ5Wf65E1EJZQky1RZ+2eO78nFhY3dCRrlTP9zSLhcmzbu72eNpR2U3x2g7LAEfBjvFdWmcbg0xbg==; Domain=account.xiaomi.com; Path=/; HttpOnly
Set-Cookie: passToken=Aq3FBlXT880Y+FyC7LB8rYE0wz8nThC2b740zWzDAUt1YZxxxxeZN2NGEYyOKnShUJfZg7dd7LB/wTuijbC8EjM39u77R0pwRfctT3Ch0C9KrD8kNnrlPDKRh3i7KdIy/9DEzfcT55zi/wtiJmjIJT7o0H17YZZp/R4RZRFSCMI3f7dKeKxHllw6jvLx/Kjrdixiyinbo8LS5rcOWeZD2g==; Domain=account.xiaomi.com; Path=/; HttpOnly
extension-pragma: {"ssecurity":"1dTV1iD5e9LEqQw+qbkrBg==","nonce":6426361413940357120,"psecurity":"pP9Cqr39PFt8eNIyHXLl8w=="}
Set-Cookie: pwdToken=1RmPRcQjADWxFwvTRY4fzsCCqoBrVb0M86ocukF/S9DUvhnPCdOp+wuR26UtCoR8hrwHf4VAFzVdxOhhSMpM8rWQ9eOWVPfDRZeiKc+Namo=; path=/
Set-Cookie: userId=123456789; domain=.xiaomi.com; path=/
Set-Cookie: userId=123456789; domain=account.xiaomi.com; path=/
Set-Cookie: pwdToken=1RmPRcQjADWxFwvTRY4fzsCCqoBrVb0M86ocukF/S9AaDMvgAvKmusbm0+XeQTpB1NsgGHSMKVu+pLZRAukqx7xyys8NZ7Rf280G8b1CvvE=; domain=account.xiaomi.com; path=/
Set-Cookie: userId=123456789; domain=.xiaomi.com; path=/
Set-Cookie: userId=123456789; domain=account.xiaomi.com; path=/
Set-Cookie: pExpireTime=-1; domain=account.xiaomi.com; path=/; secure
Set-Cookie: uLocale=zh_CN; path=/; expires=Mon, 06-Jan-2014 13:39:39 GMT
Cache-Control: no-cache
Content-Length: 806




转到主页：
GET http://www.xiaomi.com/c/service/js/categoryTree.js?ver=2221080 HTTP/1.1
Accept: application/javascript, */*;q=0.8
Referer: http://www.xiaomi.com/
Accept-Language: zh-CN
User-Agent: Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; Trident/6.0)
Accept-Encoding: gzip, deflate
Connection: Keep-Alive
DNT: 1
Host: www.xiaomi.com
Cookie: xmuuid=XMGUEST-F7525FF0-6B0B-11E3-BFA4-3F911C8DFC07;
 mstuid=1387718489085_3333;
 __utma=219621008.581528728.1387718489.1387718489.1387718489.1;
 __utmb=219621008.2.10.1387718489;
 __utmz=219621008.1387718489.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none);
 userName=13500000000;
 mstz=||1104227302;
 __utmc=219621008;
 XM_123456789_UN=CatcherX;
 passport_slh=2NqVtauh/yAe/JObarLgjekvV4Q=;
 userId=123456789



            
【以下是我在.NET中用HttpWebRequest请求的返回的报文】                
                /
                *
                    成功登录小米官网后返回的HTTP报文：
HTTP/1.1 200 OK
Server: Tengine/1.5.2
Date: Sun, 22 Dec 2013 13:23:35 GMT
Content-Type: application/json; charset=utf-8
Content-Length: 802
Connection: keep-alive
Set-Cookie: passToken=Aq3FBlXT880Y+FyC7LB8rSOHw9CUUZdChjC2fzQGqMfu4KBbJ0SQaq7KpMpOjhEpjcJy+6pe4Q85PqRJ4j3oGOYAX51n7RVgkfNjYJSYLLZ9uDmekv4OySZDPmpBrGOAkCWnUhY+ffdC4z4lu853XLx8E+74MaW1DWmRGuAltcs7WkqINvqN76MZoSNzilCCzykgTCv8xKrauSh0kX63GA==; Domain=account.xiaomi.com; Path=/; HttpOnly
Set-Cookie: passToken=Aq3FBlXT880Y+FyC7LB8rSOHw9CUUZdChjC2fzQGqMfu4KBbJ0SQaq7KpMpOjhEpjcJy+6pe4Q85PqRJ4j3oGOYAX51n7RVgkfNjYJSYLLbskgVXwlMWBKU3KH79ph1sVu8vGfdN1oX/hZs+0WtTJoa7JBd9iROXiHmU3aoLQMcQ/55So14eiSwKM7kZOn+pYp8bFeOsea17mVQBIyODuA==; Domain=account.xiaomi.com; Path=/; HttpOnly
extension-pragma: {"ssecurity":"Hu2YZFCq8/L7sl7K5IO88g==","nonce":6899786434773787648,"psecurity":"wVm8fvHUXh3ewrRyqjce2g=="}
Set-Cookie: pwdToken=1RmPRcQjADWxFwvTRY4fzsCCqoBrVb0M86ocukF/S9AYmZALdvWPL4S6KbBIhQQ5CSxwFtmKvr62h/OmL5CzwoqDYyqR/8NC4UyarHwudwQ=; path=/
Set-Cookie: userId=123456789; domain=.xiaomi.com; path=/
Set-Cookie: userId=123456789; domain=account.xiaomi.com; path=/
Set-Cookie: pExpireTime=-1; domain=account.xiaomi.com; path=/
Set-Cookie: pwdToken=1RmPRcQjADWxFwvTRY4fzsCCqoBrVb0M86ocukF/S9C3IsBDIIvaHuk/by5CzRa9tfkAF855ZOh2TPNT9BuoGv+h9nGf4x8IkbDUujiIp+0=; domain=account.xiaomi.com; path=/
Set-Cookie: userId=123456789; domain=.xiaomi.com; path=/
Set-Cookie: userId=123456789; domain=account.xiaomi.com; path=/
Set-Cookie: pExpireTime=-1; domain=account.xiaomi.com; path=/; secure
Set-Cookie: uLocale=zh_CN; path=/; expires=Mon, 06-Jan-2014 13:23:35 GMT
Cache-Control: no-cache
                *
                /
                
                
【转到主页】    小米主页：http://www.xiaomi.com/                

GET http://www.xiaomi.com/ HTTP/1.1
Accept-Language: zh-CN,zh;q=0.8
Host: www.xiaomi.com
Cookie: userId=123456789


===============================================================================================================
【分析】：成功POST数据到小米官网后，返回的cookie有很多个的域名是： domain=account.xiaomi.com
                导致了再次用HttpWebRequest去请求非account.xiaomi.com时，它只会发送这个Cookie：Cookie: userId=123456789
    

【当我故意设置为相同域名的url时，它就可以发送出去：】如：https://account.xiaomi.com/csdn

GET https://account.xiaomi.com/csdn HTTP/1.1
Accept-Language: zh-CN,zh;q=0.8
Host: account.xiaomi.com
Cookie: uLocale=zh_CN;
 JSESSIONID=aaaTv6zWPskV_g_1PRAmu;
 deviceId=wb_1928eaa7-0a80-4e80-a796-a877f22b2577;
 passToken=Aq3FBlXT880Y+FyC7LB8rR/3RQbQt+a8fTBq+aLpEM1jR4TX/ARFs6RVI/80z+skweRautAeEza1dF1+gOdrKDhVoygfMLR+pfQzw4Yppx1SU1p5cLfCPuYQ4UL0zcWqpASXWj1RblpA4yQ5JxVtF9c1NsWpO1piHrqsR2zIgVPSsait+YASTBtBoFb3B0VtfLnvaooyV9MdcfJsHi+cmQ==;
 pwdToken=1RmPRcQjADWxFwvTRY4fzsCCqoBrVb0M86ocukF/S9BqxxqOMAwJ5BwGMON5OgIzc4WIFMao7uh3DgsAtFmAWdlxNhri/uVYBoYbAoIvQya4=;
 userId=123456789;
 pExpireTime=-1;
 userId=123456789


【问题】要怎样处理可以像浏览器那样把cookie再传过去呢？
我现在的Cookie是这样处理的：

public static  CookieContainer _cookieContainer = new CookieContainer();  
.......
 
                /// <summary>
        /// 解析Cookie
        /// </summary>
        /// <param name="response"></param>
        private void ParseCookie(HttpWebResponse response)
        {
            if (!IgnoreCookies)
            {
                string cookiesExpression = response.Headers["Set-Cookie"];
                if (!string.IsNullOrEmpty(cookiesExpression))
                {
                    Uri cookieUrl = new Uri(string.Format("{0}://{1}:{2}/",
                        response.ResponseUri.Scheme,
                        response.ResponseUri.Host,
                        response.ResponseUri.Port));
                    try
                    {
                        _cookieContainer.SetCookies(cookieUrl, cookiesExpression);
                    }
                    catch
                    { }
                }
            }
        }
                
                 /// <summary>
        /// 配置请求设置
        /// </summary>
        /// <param name="request"></param>
        private void ConfigRequest(HttpWebRequest request)
        {
                        .....
            request.CookieContainer = _cookieContainer;
                        ....
        }