Snmp packet format

[C# Programming]

I am developing a Snmp utility in C# which can fetch data from a specified Oid of a device.I am using Snmp version1 packet format.I tested it on localhost and windows server in the network, it is working fine. But it is not working for routers in network.
Snmp service is running on all devices as routers reply for the snmpwalk command from putty.

Is it a packet format issue or anything else?