using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Windows.Forms;

using System.Text;

using Autodesk.Navisworks.Api.Controls;

      static public void HideUnselected()
      {
         //Create hidden collection
         ModelItemCollection hidden = new ModelItemCollection();

         //create a store for the visible items
         ModelItemCollection visible = new ModelItemCollection();

         //Add all the items that are visible to the visible collection
         foreach (ModelItem item in Autodesk.Navisworks.Api.Application.ActiveDocument.CurrentSelection.SelectedItems)
         {
            if (item.AncestorsAndSelf != null)
               visible.AddRange(item.AncestorsAndSelf);
            if (item.Descendants != null)
               visible.AddRange(item.Descendants);
         }

         //mark as invisible all the siblings of the visible items as well as the visible items
         foreach (ModelItem toShow in visible)
         {
            if (toShow.Parent != null)
            {
               hidden.AddRange(toShow.Parent.Children);
            }
         }

         //remove the visible items from the collection
         foreach (ModelItem toShow in visible)
         {
            hidden.Remove(toShow);
         }

         //hide the remaining items
         Autodesk.Navisworks.Api.Application.ActiveDocument.Models.
            SetHidden(hidden, true);
      }