MFC winInet用post方式提交数据失败

IIS服务器总是获取不到提交的数据，代码如下: char temp[128];
TCHAR szRequest[128] = _T("username=test&userpwd=test&button=%CC%E1%BD%BB");  //DWORD dwHttpRequestFlags = INTERNET_FLAG_EXISTING_CONNECT | INTERNET_FLAG_DONT_CACHE | INTERNET_FLAG_TRANSFER_BINARY;
DWORD dwHttpRequestFlags=INTERNET_FLAG_EXISTING_CONNECT;
cstrObject=_T("/login.asp?action=login");
m_pHttpFile=m_pHttpcon->OpenRequest(CHttpConnection::HTTP_VERB_POST,cstrObject,NULL,1,NULL,NULL,dwHttpRequestFlags); m_pHttpFile->AddRequestHeaders(_T("POST /login.asp?action=login HTTP/1.1"));  
m_pHttpFile->AddRequestHeaders(_T("Accept: */*"));  
m_pHttpFile->AddRequestHeaders(_T("Referer: http://localhost/login.asp"));  
m_pHttpFile->AddRequestHeaders(_T("Accept-Language: zh-cn"));  
m_pHttpFile->AddRequestHeaders(_T("User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; GTB7.3; QQDownload 718; InfoPath.3; .NET CLR 2.0.50727; MS-RTC LM 8; .NET CLR 3.0.04506.30; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; .NET CLR 1.1.4322)"));  
m_pHttpFile->AddRequestHeaders(_T("Content-Type: application/x-www-form-urlencoded"));  
m_pHttpFile->AddRequestHeaders(_T("Accept-Encoding: gzip, deflate"));  
m_pHttpFile->AddRequestHeaders(_T("Host: localhost"));  
m_pHttpFile->AddRequestHeaders(_T("Connection: Keep-Alive")); 
m_pHttpFile->AddRequestHeaders(_T("Content-Length 46"));
m_pHttpFile->AddRequestHeaders(_T("Cache-Control: no-cache"));
m_pHttpFile->AddRequestHeaders(_T("Cookie: ASPSESSIONIDQQDSTSQT=HBEFDNEAMDCDJGCDHDGICKOC"));
m_pHttpFile->AddRequestHeaders(_T("\r\n\r\n"));   
//m_pHttpFile->SendRequest(NULL, 0, (LPVOID)szRequest, _tcslen(szRequest)+1); 
CString cstrCS(_T("username=test&userpwd=test&button=%CC%E1%BD%BB"));
int lens=cstrCS.GetLength();
m_pHttpFile->SendRequest(NULL, 0, (LPVOID)cstrCS.GetBuffer(),cstrCS.GetLength());