internal class CustomContextMenuBuilder : NDiagramContextMenuBuilder
  {
   public override NContextMenu BuildContextMenu(object obj)
   {
    NContextMenu contextMenu = null;
    if (obj as NDrawingDocument == null)
    {
      contextMenu = new NContextMenu();
      /* Added Delete option in the context menu */
      contextMenu.Commands.Add(CreateCommand((int)DiagramCommand.Delete, false));

      bool isConnectorMenu = obj as NRoutableConnector != null;
      if (isConnectorMenu)
       contextMenu.Commands.Add(CreateCommand((int)DiagramCommand.Reroute, true)); /* Added Reroute option in the context menu if connectors*/

      /* Added SubmenuOrder in the context menu */
      contextMenu.Commands.Add(CreateCommand((int)DiagramCommand.SubmenuOrder, !isConnectorMenu));

      /* Added SubmenuRotateOrFlip in the context menu */
      contextMenu.Commands.Add(CreateCommand((int)DiagramCommand.SubmenuRotateOrFlip, false));

        if (offpageSystems.Count > 0)  //Lets suppose it is list of String and I am creating a Sub menu
        {
          NCommand offpageCommand = new NCommand();
          offpageCommand.Context = new NCommandContext(new NCommandProperties()
          {
           BeginGroup = true,
           ShowArrowStyle = ShowArrowStyle.Default,
           Name = "OffpageParent",
           ID = ((int)DiagramCommand.LastCommandId + 20),
           Text = "Offpage HVAC Systems"
          });         
         
          contextMenu.Commands.Add(offpageCommand);

          for (int cnt = 0; cnt < offpageSystems.Count; cnt++)
          {
           NCommand subCmd = new NCommand(new NCommandProperties()
           {
            Name = string.Format("OffpageChild{0}", cnt),
            ID = ((int)DiagramCommand.LastCommandId + 20 + cnt),
            Text = offpageSystems[cnt].SimModelName,
            Tag = offpageSystems[cnt].RowReference
           });
           offpageCommand.Commands.Add(subCmd);
          }

        }
 
     
      //DiagramCommandRange
    }
    return contextMenu;
   }