Re: selection set

Tell me if it works like a charm

#region Namespaces

using System;
using System.Text;
using System.Linq;
using System.Xml;
using System.Reflection;
using System.ComponentModel;
using System.Collections;
using System.Collections.Generic;
using System.Windows;
using System.Windows.Media.Imaging;
using System.Windows.Forms;
using System.IO;

using Autodesk.Revit.ApplicationServices;
using Autodesk.Revit.Attributes;

using Autodesk.Revit.DB;
using Autodesk.Revit.DB.Events;
using Autodesk.Revit.DB.Architecture;
using Autodesk.Revit.DB.Structure;
using Autodesk.Revit.DB.Mechanical;
using Autodesk.Revit.DB.Electrical;
using Autodesk.Revit.DB.Plumbing;

using Autodesk.Revit.UI;
using Autodesk.Revit.UI.Selection;
using Autodesk.Revit.UI.Events;

//using Autodesk.Revit.Collections;
using Autodesk.Revit.Exceptions;
using Autodesk.Revit.Utility;

using RvtApplication = Autodesk.Revit.ApplicationServices.Application;
using RvtDocument = Autodesk.Revit.DB.Document;

#endregion

namespace RevitAddinCS2
{
    [Transaction(TransactionMode.Manual)]
    [Regeneration(RegenerationOption.Manual)]
    public class ExtCmd : IExternalCommand
    {
        #region Cached Variables

        private static ExternalCommandData _cachedCmdData;

        public static UIApplication CachedUiApp
        {
            get
            {
                return _cachedCmdData.Application;
            }
        }

        public static RvtApplication CachedApp
        {
            get
            {
                return CachedUiApp.Application;
            }
        }

        public static RvtDocument CachedDoc
        {
            get
            {
                return CachedUiApp.ActiveUIDocument.Document;
            }
        }

        #endregion

        #region IExternalCommand Members

        public Result Execute(ExternalCommandData cmdData, ref string msg, ElementSet elemSet)
        {
            _cachedCmdData = cmdData;

            try
            {
                //SelectionFilterElement sf = new SelectionFilterElement();

                FilteredElementCollector collector = new FilteredElementCollector(cmdData.Application.ActiveUIDocument.Document).OfClass(typeof(Wall));
                List<Element> elements = collector.Cast<Element>().ToList();
                List<ElementId> Ids = new List<ElementId>();

                foreach (Element e in elements)
                {
                    elemSet.Insert(e);
                    Ids.Add(e.Id);
                }

                cmdData.Application.ActiveUIDocument.Selection.SetElementIds(Ids);
                return Result.Succeeded;

            }
            catch (Exception ex)
            {
                msg = ex.ToString();
                return Result.Failed;
            }
        }

        #endregion
    }
}

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