如题，我自定义了一个CRgnButton，在DrawItem方法中调用gdiplus画上了按钮的一张图片，现在想给按钮加个选中的边框。但是，Graphics的DrawImage方法起作用了，能看到图片的效果，但是Graphicse的Rectangle方法为什么画不出矩形框？
if (pImg != NULL){
Graphics g(lpDrawItemStruct->hDC);
g.SetClip(trgn, CombineModeReplace);
g.DrawImage(pImg, RectF((REAL)0, (REAL)0, (REAL)pImg->GetWidth(), (REAL)pImg->GetHeight()));
if (m_noDownAnimation == false){
g.DrawImage(pImg, RectF((REAL)m_imgOffset.X, (REAL)m_imgOffset.Y, (REAL)pImg->GetWidth(), (REAL)pImg->GetHeight()));
}
g.Flush();
SolidBrush brush(RGB(255, 255, 255));
Pen p(RGB(255, 255, 255));
p.SetWidth(2);
p.SetDashStyle(DashStyleDot);
g.DrawRectangle(&p, RectF((REAL)10, (REAL)10, (REAL)(pImg->GetWidth()-10), (REAL)(pImg->GetHeight()-10)));
g.Flush();
g.ReleaseHDC(lpDrawItemStruct->hDC);