public static DisplayItemCircle GenDisplayItemCircle(DisplayItemList list, GePoint center, double radius)
        {
            DisplayItemCircle Circle = new DisplayItemCircle(
                center, radius);
            if (list != null)
                list.AddItem(Circle);

            return Circle;
        }
 // Support the operation for selection
 protected override Manipulator OnItemSelection(DisplayItemCircle SelectedItem)
 {
     try
     {
         CircleNode Node = (CircleNode)m_Node;
         return new CircleChangeManipulator(Node);
     }
     catch
     {
         return null;
     }
 }
        public override void GenerateGraphics(DisplayItemList DLList)
        {
            if (null == DLList) return;

            if (m_dRadius < 0)
                return;

            //DisplayItemList DisplayList = new DisplayItemList();

            DisplayItemCircle Circle = new DisplayItemCircle(
                m_CenterPoint, m_dRadius);
            DLList.AddItem(Circle);

            DisplayItemPoint CenterPoint = new DisplayItemPoint(m_CenterPoint);
            DLList.AddItem(CenterPoint);
        }
 protected virtual Manipulator OnItemSelection(DisplayItemCircle SelectedItem)
 {
     return null;
 }