Перерисовка окна

LRESULT CALLBACK WindowFunc(HWND hwnd,
                            UINT message,
                            WPARAM wParam,
                            LPARAM lParam)
{
  switch(message)
  {
    case WM_CREATE:
      hdc=GetDC(hwnd);
      hdcMem = CreateCompatibleDC(hdc);
      hbmMem = CreateCompatibleBitmap(hdc, win_width, win_height);
      hOld = SelectObject(hdcMem, hbmMem);
    break;
 
        
    case WM_CHAR:
      Ellipse(hdcMem,100,100,200,200);
    break;
 
    case WM_PAINT:
 
      BitBlt(hdc, 0, 0, win_width, win_height, hdcMem, 0, 0, SRCCOPY);
    break;
 
    case WM_DESTROY:
    ReleaseDC(hwnd, hdc);
        DeleteObject(SelectObject(hdcMem,hOld));
 
        ReleaseDC(hwnd,hdcMem);
 
    PostQuitMessage(0);
      
        default:
        return DefWindowProc(hwnd,message,wParam,lParam);
  }
  return 0;
}

case WM_CREATE:
    {
      hdc=GetDC(hwnd);
      hdcMem = CreateCompatibleDC(hdc);
      hbmMem = CreateCompatibleBitmap(hdc, win_width, win_height);
      hOld = SelectObject(hdcMem, hbmMem);
      HBRUSH hBkGrnd=(HBRUSH)GetStockObject(GRAY_BRUSH);
      HBRUSH hSaveBrush=(HBRUSH)SelectObject(hdcMem,hBkGrnd);
      PatBlt(hdcMem,0,0,win_width,win_height,PATCOPY);
      DeleteObject(SelectObject(hdcMem,hBkGrnd)); 
      ReleaseDC(hwnd, hdc);
    }
    break;