LoadBitmap(), how to avoid GDI Object buildup

From:

"Harald" <Haraldnospamcollonia@yahoo.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Mon, 23 Apr 2007 13:34:34 GMT

Message-ID:

<KB2Xh.7636$3P3.3846@newsread3.news.pas.earthlink.net>

VS 2005, MFC Dialog-based app. I am drawing a diagram and, depending on a
condition, add one of three bitmaps to the diagram. How do I properly
release the bitmaps when I exit the dialog? Here is the code I am using, and
the bitmaps are released, but the code in OnDestroy() looks strange to me.

// load the bitmaps
BOOL CMyDialog::On InitDialog()
{
    ....
    bmp1.LoadBitap("Bitmap1");
    bmp2.LoadBitmap("Bitmap2");
    bmp3.LoadBitmap("Bitmap3");
    ....
}

void CMyDialog::OnPaint()
{
    CDC MemDC;
    MemDC.CreateCompatibleDC(&dc);
    CBitmap Bmp;
    Bmp.CreateCompatibleBitmap(&dc,size_a,size_b);
    CBitmap *pOldBmp = MemDC.SelectObject(&Bmp);
    DrawDiagram(&memDC);

    // add one of three bitmaps based on condition
    CDC tempDC;
    tempDC.CreateCompatibleDC(&tempDC);
    if (m_condition==1)
        tempDC.SelectObject(&bmp1);
    if(m_condition==2)
        tempDC.SelectObject(&bmp2);
    else
        tempDC.SelectObject(&bmp3);
    MemDC.BitBlt(position_c,position_d,24,20,&tempDC,0,0,SRCCOPY);

// now draw the combined graphics to screen
    dc.BitBlt(0,0,
    aa,cc,&MemDC,0,0,SRCCOPY);

    MemDC.SelectObject(pOldBmp);
}

// clean up
void CMyDialog::OnDestroy()
{
    DeleteObject(bvmp1);
    DeleteObject(bvmp2);
    DeleteObject(bvmp3);

    bmp1.Detach();
    bmp2.Detach();
    bmp2.Detach();
}

My question is: How do I properly clean up the GDI objects bmp1, bmp2, bmp3?
The way I do it in OnDestroy() works, but it looks strange to me. Thanks for
your comments.

Harald