I'm not sure if I understand what exactly you want to do.
Guess you know the great SNMP-tool 'Net-SNMP' (http://www.net-snmp.org/)?
To identify a device-type use the sysObjectID(1.3.6.1.2.1.1.2.0
):
snmpget -v 1 -c YourSecret 192.168.1.1 1.3.6.1.2.1.1.2.0
The response-value is an OID which identifies the device type.
You don't need to login but use the right community-string (in my example 'YourSecret').
SnmpWalk is equivalent to the GetNext-Command.
I you rather develop something yourself in Visual Basic I can also give you some advise because that's exactly what I did.
Regards
Rolf