I am trying to maintain a list of certain code lock to run additional code when the CanUseLockedEntity is called, but I want to validate it is a code lock that I have preselected. I tried GetInstanceId() but that changed on reboot.

Use NET ID (Network ID, qnique)

entity.net.ID​ // its uint value

So I tried that and it seems to change after reboot. I run it write down the number and run it. Reboot the server go click the same door and get a different number.

 bool CanUseLockedEntity(BasePlayer player, BaseLock baseLock)
        {

            BroadcastMessage("Oh Oh");
            CodeLock codelock = baseLock as CodeLock;

            BroadcastMessage(player.displayName + " jsut touched me in the " + codelock.net.ID);
            return true;
        }​

1. You dont need to get CodeLock from BaseLock. You can just get net id from Baselock.
2. Its no way, because net ID is unique, and it didnt changing.