Inheritance: System.MarshalByRefObject, IVertex
		private void RemoveDependent(GraphNode graphNode)
		{
			Outgoing.Remove(graphNode);
		}
		public void AddDependent(GraphNode node)
		{
			Outgoing.Add(node);
			node.Incoming.Add(this);
		}
		public void RemoveDepender(GraphNode depender)
		{
			Incoming.Remove(depender);
			depender.RemoveDependent(this);
		}