CListCtrl

int nItem;
_variant_t vUsername,vBirthday,vID,vOld;
nItem=m_userlist.InsertItem(0xffff,(_bstr_t)vID);
m_userlist.SetItem(nItem,1,1,(_bstr_t)vUsername,NULL,0,0,0);
m_userlist.SetItem(nItem,2,1,(_bstr_t)vOld,NULL,0,0,0);
m_userlist.SetItem(nItem,3,1,(_bstr_t)vBirthday,NULL,0,0,0);
请问在m_userlist.InsertItem()中0xfffff代表什么意思啊？