vc做的MFC控件找不到控件自己的句柄,或返回0

m_hWnd直接调用是没问题的，但是调用的时机不对，应增加下面方法：

void CxxxCtrl::OnSetClientSite()
   {
      if (m_pClientSite)
         // It doesn't matter who the parent window is or what the size of
         // the window is because the control's window will be reparented
         // and resized correctly later when it's in-place activated.
         VERIFY (CreateControlWindow (::GetDesktopWindow(), CRect(0,0,0,0),
                                      CRect(0,0,0,0)));
      COleControl::OnSetClientSite();
   }