integrate Revit 2025 SDK

SDK/Samples/AddSpaceAndZone/CS/ZoneNode.cs

@@ -1,5 +1,5 @@
 //
-// (C) Copyright 2003-2019 by Autodesk, Inc.
+// (C) Copyright 2003-2023 by Autodesk, Inc.
 //
 // Permission to use, copy, modify, and distribute this software in
 // object code form for any purpose and without fee is hereby granted,
@@ -21,10 +21,7 @@
 // 
 
 using System;
-using System.Collections.Generic;
-using System.Text;
 using System.Windows.Forms;
-using Autodesk.Revit.DB;
 using Autodesk.Revit.DB.Mechanical;
 
 namespace Revit.SDK.Samples.AddSpaceAndZone.CS
@@ -34,6 +31,7 @@ namespace Revit.SDK.Samples.AddSpaceAndZone.CS
     /// to display the Zones is a TreeView, each ZoneNode contains
     /// a Zone element.
     /// </summary>
+    [Serializable]
     public class ZoneNode : TreeNode
     {
         Zone m_zone;