为什么我要查询的数据在设的列表控件中显示不出来
有两个查询按钮和显示的函数
void CSs3View::OnButton1()
{UpdateData(TRUE);
// TODO: Add your control notification handler code here
choice=1;

show(m_checkbynum);
m_checkbysub="";
UpdateData(FALSE);
}

void CSs3View::OnButton2()
{UpdateData(TRUE);
// TODO: Add your control notification handler code here
choice=2;

show(m_checkbysub);
m_checkbynum="";
UpdateData(FALSE);
}

void CSs3View::show(CString s)
{
CString str;
while(myshowlist.GetItemText(Data)>0)
{myshowlist.DeleteString(0);
}
m_pSet->MoveFirst();
while(m_pSet->IsEOF()!=1)
{switch(choice)
{
case 1:
{
if(m_pSet->m_studentnum==s)
{
str.Format ("%8s%8s%6s%6f",m_pSet->m_studentnum ,m_pSet->m_studentname,
m_pSet->m_subject,m_pSet->m_mark);
myshowlist.AddString(str);
m_pSet->MoveNext ();
myshowlist.UpdateData(FALSE);
}
else
m_pSet->MoveNext ();
}
break;
case 2:
{
if(m_pSet->m_subject==s)
{if(m_pSet->m_mark <60)
less60++;
else if(m_pSet->m_mark <70)
between60to70++;
else if(m_pSet->m_mark <80)
between70to80++;
else if(m_pSet->m_mark <90)
between80to90++;
else
than90++;
str.Format ("%8s%8s%6s%6f",m_pSet->m_studentnum ,m_pSet->m_studentname,
m_pSet->m_subject,m_pSet->m_mark);
myshowlist.AddString(str);
m_pSet->MoveNext ();
UpdateData(FALSE);
}
else
m_pSet->MoveNext ();
}
break;
}
}

}