windows phone 7 - Post ampersand character to HttpWebRequest -

i need pass string server contains 1 or few value. api grammar following:

 &track=name or  &track=name&artist=name 

however server return blank string. if remove char &, server return thing this: "�\b\0\0\0\0\0\0\0�zi��f��ϯ��

            string post = "track=love";        // post = post.replace("&", "%26");     //    httputility.urlencode(post); 

what should do? should have & char included or need read result server? code follow:

       protected override void onnavigatedto(system.windows.navigation.navigationeventargs e)     {         s = navigationcontext.querystring["parameter1"];   //      string strconnecturl = "http://mp3.rolo.vn/mp3/search";         try         {              httpwebrequest webrequest = (httpwebrequest)webrequest.create(strconnecturl);             webrequest.method = "post";             webrequest.contenttype = "application/x-www-form-urlencoded;charset=utf-8";             // start asynchronous operation             webrequest.begingetrequeststream(new asynccallback(getrequeststreamcallback), webrequest);         }         catch (exception ex)         {             messagebox.show(ex.tostring());         }     }      private static void getrequeststreamcallback(iasyncresult asynchronousresult)     {         string post = "track=love";          try         {             httpwebrequest request = (httpwebrequest)asynchronousresult.asyncstate;              // end operation             stream poststream = request.endgetrequeststream(asynchronousresult);              // convert string byte array.             byte[] postbytes = encoding.utf8.getbytes(post);              // write request stream.             poststream.write(postbytes, 0, postbytes.length);             poststream.close();              // start asynchronous operation response             request.begingetresponse(new asynccallback(getresponsecallback), request);         }         catch (exception ex)         {             messagebox.show(ex.tostring());         }     }  //      static stream str;     static string st;     private static void getresponsecallback(iasyncresult asynchronousresult)     {               httpwebrequest request = (httpwebrequest)asynchronousresult.asyncstate;              // end operation             httpwebresponse response = (httpwebresponse)request.endgetresponse(asynchronousresult);             httpstatuscode rcode = response.statuscode;             stream streamresponse = response.getresponsestream();              streamreader streamread = new streamreader(streamresponse);          //this return "" value, expect return xml string                            st = streamread.readtoend();             //console.writeline(responsestring);             // close stream object             streamresponse.close();             streamread.close();             // release httpwebresponse             response.close();       } 

it's form post, use ampersand separate key values: track=name&artist=name

" "�\b\0\0\0\0\0\0\0�zi��f��ϯ��" -> looks result compressed.