please,Help me!!

sorry.I don't speak well.
my code
void CSimpleExAppView::Draw( const TRect& /*aRect*/ ) const
    {
    // Get the standard graphics context
    CWindowGc& gc = SystemGc();
   const CFont*   font;
   TRect   drawRect=Rect();
    // Gets the control's extent
    //TRect drawRect( Rect());
   //HeightInPixels())/
    // Clears the screen
    gc.Clear( drawRect );
    font=iEikonEnv->TitleFont();
    gc.UseFont(font);
    TInt baselineOffset=(drawRect.Height() - font->HeightInPixels())/2;
    gc.DrawText(_L("Simple Text Draw"),drawRect,baselineOffset,CGraphicsContext::ECenter,0);
    gc.DiscardFont();
     }


when complier have one err.this is error.
"
Severity   Description   Resource   In Folder   Location   Creation Time   Id
2   Undefined symbol: 'int CFont::HeightInPixels(void) const (?HeightInPixels@CFont@@QBEHXZ)' referenced from 'void CSimpleExAppView::Draw(class TRect const &) const (?Draw@CSimpleExAppView@@UBEXABVTRect@@@Z)' in SimpleExAppView.cpp:99   SimpleEx      line 0   January 3, 2004 3:06:29 PM   1065
"

Thank you.
utcuong3010.Vietnam.