dc.LineTo not drawing on OnPaint() unless I move the use the mouse and move the window out of view?

Unless I make "static CPaintDC dc(this);" the line won't draw? But this is not good as it will eventually error, also the graphics wont' keep on the screen.

Not sure what I am doing wrong

Note: I have a Timer that calls to this every 100ms(x and y are incremented)
thx

void CGraphicsDlg::OnPaint() 
 {
     CString s;
     CPaintDC dc(this);// device context for painting
 
     if (IsIconic())
     {
         SendMessage(WM_ICONERASEBKGND, (WPARAM) dc.GetSafeHdc(), 0);
 
         // Center icon in client rectangle
         int cxIcon = GetSystemMetrics(SM_CXICON);
         int cyIcon = GetSystemMetrics(SM_CYICON);
         CRect rect;
         GetClientRect(&rect);
         int x = (rect.Width() - cxIcon + 1) / 2;
         int y = (rect.Height() - cyIcon + 1) / 2;
 
         // Draw the icon
         dc.DrawIcon(x, y, m_hIcon);
     }
     else if(x==0)
     {
         s.Format("%d", x);
         edXa->SetWindowText(s);
 
         dc.MoveTo(20,400);
     }
     else if (x>0){
         s.Format("%d", x);
         edXb->SetWindowText(s);
 
         dc.LineTo(20 + x, 40);  // doesn't draw unless I make "static CPaintDC dc(this);" <- which will error out 
     }
     CDialog::OnPaint();
 }
 
 void CGraphicsDlg::OnTimer(UINT nIDEvent)
 {
     if(nIDEvent==1){
         srand( (unsigned)time( NULL ) );
 
         //y = rand() % 100;
         y++;
         x++;
 
         OnPaint();
     }
 }
 

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