DrawDragRect函数在窗口显示异常

DrawDragRect函数在窗口显示异常：

父窗口风格设置异常；

    SetWindowLongPtr(m_hWnd,
        GWL_EXSTYLE,
        GetWindowLong(m_hWnd, GWL_EXSTYLE) | WS_EX_LAYERED);

去除这段代码就OK显示正常了

下面附上画选中矩形框的代码；

void OnLButtonDown(UINT nFlags, CPoint point)
{
        SetCapture();
        m_bDragging = true;
        m_lastPoint = point;
        CDC *pDC = GetDC();
        CRect rect(point, point);
        pDC->DrawDragRect(&rect, CSize(1, 1), NULL, CSize(1, 1), NULL, NULL);
        m_lastRect = rect;
        ReleaseDC(pDC);
}
void OnMouseMove(UINT nFlags, CPoint point)
{    
    if (m_bDragging && GetCapture() == this)
    {
        CDC *pDC = GetDC();
        CSize curSize(1,1), lastSize;
        CRect newRect(m_lastPoint, point);
        newRect.NormalizeRect();
        lastSize.cx = 1;
        lastSize.cy = 1;
        pDC->DrawDragRect(newRect, curSize, m_lastRect, lastSize);
        ReleaseDC(pDC);
        m_lastRect = newRect; 
    }
}

void OnLButtonUp(UINT nFlags, CPoint point)
{
    if (m_bDragging && GetCapture() == this)
    {
        m_bDragging = false;
        CDC *pDC = GetDC();
        CRect rect(0, 0, 0, 0);
        pDC->DrawDragRect(rect, CSize(1, 1), &m_lastRect, CSize(1, 1), NULL, NULL);
        ReleaseDC(pDC);
        //Invalidate();
        ReleaseCapture();
    }
}