Can't get primarykey list using ado openschema

[eagleinfly]

I'm trying to get primary key list from db2 using ado, but it doesn't
work since pRstSchema->adoEOF always return true when I connect to db2
while it works with access and sql server. I have tried using adox to
get the key, but still failed.

Anyone could help? advance thanks!

_ConnectionPtr m_connPtr;
_RecordsetPtr pRstSchema;
try{
if (FAILED(m_connPtr.CreateInstance(__uuidof(Connecti on))) ){
return ;
}

if (FAILED(m_connPtr->Open(_bstr_t(host), "", "", -1))){
return ;
}

pRstSchema = m_connPtr->OpenSchema(adSchemaPrimaryKeys);

for(; !pRstSchema->adoEOF; pRstSchema->MoveNext())
{
//some code here, but never reach this place when i using db2
//but it works fine for access and sql server.
}
}catch(_com_error e){
//something
}catch(...){
//something
}