c# - What's wrong with my HttpWebRequest POST Request -

i have trouble while sending post http packages website, in sniffer looks http://data2.floomby.com/files/previews/25_3_2013/kui91gedh02qmem94lqtw.jpg @ screenshot. think, mixing post content data before sends, postdata string looks normal. here method code:

    public responsedata advancedrequest(string method, string url, string postdata, string proxydata, string referer, int timeout)     {         var req = webrequest.create(url) httpwebrequest;         req.method = "get";         iwebproxy myproxy = new webproxy(proxydata.split(':')[0],  convert.toint32(proxydata.split(':')[1]));         req.proxy = null;         //req.servicepoint.connectionlimit = 1;         req.protocolversion = httpversion.version10;         req.keepalive = true;         //req.useragent = "mozilla/5.0 (windows nt 6.1; wow64; rv:19.0) gecko/20100101 firefox/19.0";         req.useragent = "mozilla/5.0 (windows nt 6.1; wow64; rv:19.0) gecko/20100101 firefox/19.0";         req.allowautoredirect = false;         req.timeout = timeout*1000;         req.readwritetimeout = timeout*1000;         req.contenttype = "application/x-www-form-urlencoded";         req.accept = "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8";         req.headers.add("accept-language", "en-us,en;q=0.5");         //req.headers.add("accept-charset", "iso-8859-1,utf-8;q=0.7,*;q=0.3");         req.headers.add("accept-encoding", "gzip, deflate");         //req.headers.add("cache-control", "max-age=0");         req.cookiecontainer = _cookies;         //req.headers.add("keep-alive", "115");         //req.connection = "keepalive";         if (!string.isnullorempty(referer))         {             req.referer = referer;         }          req.automaticdecompression = decompressionmethods.gzip | decompressionmethods.deflate;         if (method == "post")         {             req.method = "post";             req.servicepoint.expect100continue = false;             system.text.encoding enc = system.text.encoding.utf8;             var bytedata = enc.getbytes(postdata);             req.contentlength = bytedata.length;             //stream poststream = req.getrequeststream();             try             {                 using (var poststream = req.getrequeststream())                 {                     poststream.write(bytedata, 0, bytedata.length);                     poststream.close();                 }             }             catch (webexception except)             {              }          }          httpwebresponse resp = (httpwebresponse)req.getresponse() httpwebresponse;         this._cookies.add(resp.cookies);         //resp.close();         responsedata rdata = new responsedata(resp);         resp.close();         return rdata;         //streamreader strdr = new streamreader(resp.getresponsestream());         //string response = strdr.readtoend();         //strdr.close();          //return response;     } 

here right post data:

session%5busername_or_email%5d=loginhere&session%5bpassword%5d=passwordhere&return_to_ssl=true&scribe_log=&redirect_after_login=%2f&authenticity_token=auth_token_here

here wrong post data have:

session%5busername_or_email%5d=asynccallback&session%5bpassword%5d=de2zmcc6093&return_to_ssl=true&scribe_log=&redirect_after_login=%2f&authenticity_token=0e67f8df715c79f81a9b2be203848ad7f805b21csession%5busername_or_email%5d=asynccallback&session%5bpassword%5d=de2zmcc6093&return_to_ssl=true&scribe_log=&redirect_after_login=%2f&authenticity_token=0e67f8df715c79f81a9b2be203848ad7f805b21c

the value of postdata is:

session%5busername_or_email%5d=login&session%5bpassword%5d=password&return_to_ssl=true&scribe_log=&redirect_after_login=%2f&authenticity_token=0e67f8df715c79f81a9b2be203848ad7f805b21c