/// <summary>
 /// Not supported.
 /// </summary>
 /// <param name="con"></param>
 protected override void OnRelativeChildShapeElementAdded(NodeShapeReferencesRelativeChildren con)
 {
     throw new NotSupportedException();
 }
        /// <summary>
        /// Called whenever a relationship of type NodeShapeReferencesRelativeChildren is added and
        /// the element hosted by this model is the source.
        /// </summary>
        /// <param name="con"></param>
        protected virtual void OnRelativeChildShapeElementAdded(NodeShapeReferencesRelativeChildren con)
        {
            if (IsDisplayingNodeShape(con.ChildShape))
                return;

            DiagramItemElementViewModel vm = this.ViewModelStore.Factory.CreateDiagramItemViewModel(con.ChildShape.GetDomainClassId(), this.Diagram, con.ChildShape);
            this.AddRelativeChild(vm);
        }