아래와 같이 간단한 소스인데 폼에는 선을 긋는데 PaintBox에는 선을 안그리네요. 가르쳐 주셔요....

type
  TForm1 = class(TForm)
    PaintBox1: TPaintBox;
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure PaintBox1Paint(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
    dc: HDC;
    dc2: HDC;
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.Button1Click(Sender: TObject);
begin
  LineTo(dc, 100, 100);
  LineTo(dc2, 100, 100);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  dc:= GetDC(PaintBox1.Canvas.Handle);
  dc2:= GetDC(self.Handle);
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  ReleaseDC(PaintBox1.Canvas.Handle, dc);
  ReleaseDC(self.Handle, dc2);
end;

procedure TForm1.PaintBox1Paint(Sender: TObject);
begin
  LineTo(dc, 100, 100);
  LineTo(dc2, 100, 100);
end;