在对话框中绘图的问题

[yibuyisheng]

为什么我用这段代码在对话框内部绘图总是运行的时候出错？！
CBrush brush,*oldBrush = NULL;
CBitmap bm[4];
bm[1].LoadBitmap(IDB_BITMAP1);
bm[2].LoadBitmap(IDB_BITMAP2);
bm[3].LoadBitmap(IDB_BITMAP3);
bm[4].LoadBitmap(IDB_BITMAP4);
CClientDC dc(this);

m_nCount++;
CRect rect;
rect.left = 0;
rect.top = 0;
rect.bottom = ::GetSystemMetrics(SM_CXSCREEN);
rect.right = ::GetSystemMetrics(SM_CYSCREEN);

CDC dcMem;
dcMem.CreateCompatibleDC(&dc);
BITMAP bitmap;
CBitmap *pbmpOld;

switch(m_nCount)
{
case 1:
bm[1].GetBitmap(&bitmap);
pbmpOld = dcMem.SelectObject(&bm[1]);
dc.StretchBlt(0,0,rect.Width(),rect.Height(),&dcMem,0,0,bitmap.bmWidth,bitmap.bmHeight,SRCCOPY);

case 2:
bm[2].GetBitmap(&bitmap);
pbmpOld = dcMem.SelectObject(&bm[2]);
dc.StretchBlt(0,0,rect.Width(),rect.Height(),&dcMem,0,0,bitmap.bmWidth,bitmap.bmHeight,SRCCOPY);

case 3:
bm[3].GetBitmap(&bitmap);
pbmpOld = dcMem.SelectObject(&bm[3]);
dc.StretchBlt(0,0,rect.Width(),rect.Height(),&dcMem,0,0,bitmap.bmWidth,bitmap.bmHeight,SRCCOPY);

case 4:
bm[4].GetBitmap(&bitmap);
pbmpOld = dcMem.SelectObject(&bm[4]);
dc.StretchBlt(0,0,rect.Width(),rect.Height(),&dcMem,0,0,bitmap.bmWidth,bitmap.bmHeight,SRCCOPY);

case 5:
m_nCount = 0;

[huziwu]

出什么错误？
还有你的case没有跟break;所以所有case条件都执行了

[Eleven]

CBitmap bm[4];
bm[1].LoadBitmap(IDB_BITMAP1);
bm[2].LoadBitmap(IDB_BITMAP2);
bm[3].LoadBitmap(IDB_BITMAP3);
bm[4].LoadBitmap(IDB_BITMAP4);

其它没看，这里数组溢出了，大兄弟。。。