void CEx_DlgDrawDlg::DoDrawCtrl()
{
CWnd *pWnd = GetDlgItem( IDC_DRAW );
CDC* pDC = pWnd->GetDC();
CRect rcClient;
pWnd->GetClientRect( rcClient ); // 获取控件客户区大小
UpdateWindow(); // 告诉对话框,控件已更新过
CBrush brush(HS_CROSS,RGB(0,0,255));
CBrush *oldBrush = pDC->SelectObject( &brush );
pDC->Rectangle( rcClient );
pDC->SelectObject( oldBrush );
}