You need to use the 'CComboBox::InsertString' method instead of 'CComboBox::AddString' method, see -
MS Learn | CComboBox Class[
^]
Your code should be -
for (INT_PTR nInd = 0; nInd < nNum; nInd++) {
int index = combo_lin.InsertString(nInd, theApp.m_arrL[nInd].m_strName);
if (index == CB_ERR) {
}
str = theApp.m_arrL[nInd].m_strName;
}