如何创建子窗口(SDK)

m_createStruct.dwExStyle=WS_VISIBLE|WS_CAPTION|WS_CHILD; m_createStruct.hwndParent=fwParent.getWndHandle(); //id是子窗口的id,为1 m_createStruct.hMenu=(HMENU)id; //用HMENU设置子窗口的ID老是不成功m_hWnd=::CreateWindow( m_createStruct.lpszClass, m_createStruct.lpszName, m_createStruct.style, m_createStruct.x, m_createStruct.y, m_createStruct.cx, m_createStruct.cy, m_createStruct.hwndParent, m_createStruct.hMenu, m_createStruct.hInstance, m_createStruct.lpCreateParams); int err=::GetLastError();为什么CreateWindow之后会m_hWnd还是0,err为1401,无效的菜单句柄。用id567后,GetLastError得到6,The handle is invalid.