Hi Steve,

the common way is to check the id of the node which is opened and regarding to that id return the child nodes.

That is looking something like that:

if (id == global::Umbraco.Core.Constants.System.Root.ToInvariantString())
        {
            var tree = new TreeNodeCollection();
            tree.Add(CreateTreeNode("calendarTree", id, queryStrings, "Calendar", "icon-calendar-alt", true, FormDataCollectionExtensions.GetValue<string>(queryStrings, "application") + StringExtensions.EnsureStartsWith(this.TreeAlias, '/') + "/overviewCalendar/all"));
            }
            return tree;
        }

        if (id == "calendarTree")
        {
            var tree = new TreeNodeCollection();

            List<ECalendar> calendar = new List<ECalendar>();

            if (Security.CurrentUser.UserType.Alias.ToLower() == "admin")
            {
                calendar = CalendarService.GetAllCalendar().ToList();
            }
            else
            {
                calendar = CalendarService.GetCalendarForUser(Security.GetUserId()).ToList();
            }
            foreach (var cal in calendar)
            {
                tree.Add(CreateTreeNode("c-" + cal.Id.ToString(), id, queryStrings, cal.Calendarname, "icon-calendar", true, FormDataCollectionExtensions.GetValue<string>(queryStrings, "application") + StringExtensions.EnsureStartsWith(this.TreeAlias, '/') + "/editCalendar/" + cal.Id));
            }
            return tree;
        }

Thas just copy paste from a package I develop but I hope it gets you the idea. The calendar are loaded from a service directly from the database.

Regards David

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