我在 int CMainFrame::OnCreate(LPCREATESTRUCT lpCreateStruct) 加入 一条语句就有错误？

请教：

我在 int CMainFrame::OnCreate(LPCREATESTRUCT lpCreateStruct) 加入
if (!m_wndDlgBar.Create(this,IDD_MYDIALOG,CBRS_TOP | CBRS_BOTTOM ,AFX_IDW_DIALOGBAR))
{
}


nt CMainFrame::OnCreate(LPCREATESTRUCT lpCreateStruct)
{
if (CFrameWnd::OnCreate(lpCreateStruct) == -1)
return -1;

if (!m_wndToolBar.CreateEx(this, TBSTYLE_FLAT, WS_CHILD | WS_VISIBLE | CBRS_TOP
| CBRS_GRIPPER | CBRS_TOOLTIPS | CBRS_FLYBY | CBRS_SIZE_DYNAMIC) ||
!m_wndToolBar.LoadToolBar(IDR_MAINFRAME))
{
TRACE0("Failed to create toolbar\n");
return -1; // fail to create
}

if (!m_wndStatusBar.Create(this) ||
!m_wndStatusBar.SetIndicators(indicators,
sizeof(indicators)/sizeof(UINT)))
{
TRACE0("Failed to create status bar\n");
return -1; // fail to create
}

if (!m_wndDlgBar.Create(this,IDD_MYDIALOG,CBRS_TOP | CBRS_BOTTOM ,AFX_IDW_DIALOGBAR))
{
}
// TODO: Delete these three lines if you don't want the toolbar to
// be dockable
m_wndToolBar.EnableDocking(CBRS_ALIGN_ANY);
EnableDocking(CBRS_ALIGN_ANY);
DockControlBar(&m_wndToolBar);

return 0;
}


编译时提示的错误是：
--------------------Configuration: Mypro31 - Win32 Debug--------------------
Compiling...
MainFrm.cpp
C:\Program Files\Microsoft Visual Studio\MyProjects\Mypro31\MainFrm.cpp(70) : error C2065: 'IDD_MYDIALOG' : undeclared identifier
Error executing cl.exe.

Mypro31.exe - 1 error(s), 0 warning(s)



这是为什么啊？