private Node GetNode(GDMIndividualRecord iRec)
{
long nodeId = (iRec != null) ? iRec.GetId() : --fLastUnknownId;
Node node = fNodes.Find(nd => (nd.Id == nodeId));
if (node == null)
{
node = new Node(this, nodeId, iRec);
fNodes.Add(node);
}
return(node);
}