当没设置CBS_NOINTEGRALHEIGHT时，5.0会算一个比较合适的滚动条，而6.0几乎会全展开(一直到屏幕边缘显示不下才有滚动条)。
void ResizeComboBoxHeight(CComboBox &combo, int lines) { CRect cbsize; // current size of the combo box int height; // new height combo.GetClientRect(&cbsize); // Compute the new height. height = combo.GetItemHeight(-1); height += combo.GetItemHeight(0)*lines; height += GetSystemMetrics(SM_CYEDGE)*4; // top and botton edges for editbox and dropdown box combo.SetWindowPos(NULL,0,0,cbsize.right,height,SWP_NOMOVE | SWP_NOZORDER); }