Why doesn’t my CXTPPropertyGrid work?

I want to add CXTPPropertyGrid to a dialog,but it displays nothing!!

////////////////////////////////////////////////
 DDX_Control(pDX, IDC_RECT, m_rect);
////////////////////////////////////////////////
CRect rc;
m_rect.GetWindowRect( &rc );
ScreenToClient( &rc );

m_wndPropertyGrid.Create( rc, this, 0 );
CXTPPropertyGridItem* pSettings        = m_wndPropertyGrid.AddCategory(_T("Document Settings"));

CXTPPropertyGridItem* pItemSaveOnClose = pSettings->AddChildItem(new CXTPPropertyGridItemBool(_T("SaveOnClose"), TRUE));
pSettings->Expand();
///////////////////////////////////////////////