MFC- GetPixel doesn't work!!!

In an SDI application I created a new Class, say, CTest. In one of the member functions of CTest I included the following code -

void CTest::SomeFunc(...)
{
  ...
     int x;
     int y;
  
  ...
  
  CFrameWnd* pFrame = (CFrameWnd*)(AfxGetApp()->m_pMainWnd);
  CMyAppView* pView = (CMyAppView*)(pFrame->GetActiveView());

  CClientDC dc(pView);

  COLORREF pix = dc.GetPixel(x, y);

  ...
}
 

But the function GetPixel doent return the correct value of the the pixel color at (x,y); when I debugged it pix always had the value 0xffffffff. Please help... "There is a Bug in every Code!"