MFC 浮动面板在对话框窗体上创建不了，报错，怎么解决？

部分代码

CDockablePane* m_dockablePane;

int CWindows::OnCreate(LPCREATESTRUCT lpCreateStruct)

{

if (CDialogEx::OnCreate(lpCreateStruct) == -1)

	return -1;

CClientDC dc(this);

m_cellwidth = dc.GetDeviceCaps(LOGPIXELSX);

m_cellheight = dc.GetDeviceCaps(LOGPIXELSY);

m_nRiroboWidth = m_cellwidth / 2;

m_nRiroboHeight = m_cellheight / 2;

m_nVeiwWidth = (m_cellwidth * 100)+m_nRiroboWidth;

m_nVeiwHeight = m_cellheight * 10;

// TODO:  在此添加您专用的创建代码

m_dockablePane = new CDockablePane();

m_dockablePane->Create(_T("元件栏"), this, CRect(0, 0, 200, 100), TRUE, 1, WS_CHILD | WS_VISIBLE | CBRS_TOP);

return 0;

}

请高手指教？