Winform 向某 jsp 提交数据,模仿 submit 不成功,不知何故?

有一jsp页面,代码类似下面:<%
String content = request.getParameter("content");
%><FORM name=sendform action=./smstest.jsp method=post>
     <tr>
        <td>content<input name="content" maxLength=160 value=<%=content%>/></td>
         <td><INPUT value="ok" type=submit ></td>
      </tr>
</FORM>smstest.jsp就是本身现在我在winform里提交这样的参数---------------------------
content=aa&feeCode=1000&feeType=1
---------------------------
public static string url = "../smstest.jsp" ;
public static string PostData( string str)
{
try
{ byte[] data = System.Text.Encoding.GetEncoding ("GB2312").GetBytes ( str ) ;
// 准备请求...
HttpWebRequest req = (HttpWebRequest) WebRequest.Create ( url ) ; 
req.Method = "Post" ;
req.ContentType ="application/x-www-form-urlencoded";
req.ContentLength = data.Length ;
Stream stream = req.GetRequestStream () ; //获得请求流 
// 发送数据
stream.Write ( data ,0 ,data.Length ) ;
stream.Close () ;

HttpWebResponse rep = (HttpWebResponse)req.GetResponse();
Stream receiveStream = rep.GetResponseStream();
Encoding encode = System.Text.Encoding.GetEncoding("GB2312"); StreamReader readStream = new StreamReader( receiveStream, encode ); Char[] read = new Char[256];
int count = readStream.Read( read, 0, 256 );
StringBuilder sb = new StringBuilder ("") ;
while (count > 0) 
{
String readstr = new String(read, 0, count);
sb.Append ( readstr ) ;
count = readStream.Read(read, 0, 256);
}

rep.Close();
readStream.Close(); return sb.ToString () ; }}
可以返回jsp页面的html内容,但是不执行submit事件,不知道错在哪???仔细看过http://lovecherry.cnblogs.com/archive/2005/04/22/143341.html
和http://community.csdn.net/Expert/topic/4272/4272342.xml?temp=.2274897
还是没解决....