public bool IsMemberValid( NodeType groupnodedata, NodeType membernodedata, bool ignoreexistingmembership )
Parameters
- groupnodedata
 - the node data that is a group
 - membernodedata
 - a node data
 - ignoreexistingmembership
 - whether to ignore the membernodedata's existing group membership, because that member is being transferred out of its existing group