Finally, i found it for my self:
INetworkAdapter *adpt = NULL;
rc = iMachine->GetNetworkAdapter(0, &adpt);
rc = adpt->put_Enabled(TRUE);
rc = adpt->put_AttachmentType(NetworkAttachmentType_HostOnly);
rc = iMachine->SaveSettings();
This adds Host_only Network Adapter to the Guest Machine in Virtual Box.