[WebMethod]
public string UploadFile(byte[] data)

static TCHAR hdrs[] = "Content-Type: application/x-www-form-urlencoded";
     static TCHAR frmdata[] = "data=temp.txt";
  HINTERNET hSession = InternetOpen("MyAgent",INTERNET_OPEN_TYPE_PRECONFIG, NULL, NULL, 0);
  HINTERNET hConnect = InternetConnect(hSession, "localhost",
      INTERNET_DEFAULT_HTTP_PORT, NULL, NULL, INTERNET_SERVICE_HTTP, 0, 1);
  HINTERNET hRequest = HttpOpenRequest(hConnect, "POST", "my/WebService.asmx/UploadFile", NULL, NULL, 0, 0, 1);
  HttpSendRequest(hRequest, hdrs, strlen(hdrs), frmdata, strlen(frmdata));