RadTreeList - Expand Items Stored on Session

[Diego]

Hi,

I need to restore the expanded state of a RadTreeList after a redirect. I am storing the expanded items in Session before the redirect. However, server-side expansion only expands the root, not the child items.

Can someone share a JavaScript example or approach to fully expand all previously expanded nodes by the user after a redirect using the stored session data?

If your approach works in Server Side, I will use it on my solution

Thanks team!

This is an example using server side, but it expands only the first root element (not sure why)

using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using Telerik.Web.UI;

namespace SysMgmt.Groups
{
    public partial class GroupMaintenanceServer : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                RadTreeList1.NeedDataSource += RadTreeList1_NeedDataSource;
            }
        }

        protected void RadTreeList1_NeedDataSource(object sender, TreeListNeedDataSourceEventArgs e)
        {
            RadTreeList1.DataSource = GetData();
        }

        // ✅ Guardar los nodos expandidos antes del render
        protected void Page_PreRender(object sender, EventArgs e)
        {
            var expandedItems = RadTreeList1.Items
                .Where(i => i.Expanded)
                .Select(i => (int)i.GetDataKeyValue("ID"))
                .ToList();

            Session["ExpandedNodes"] = expandedItems;
        }

        protected void RadTreeList1_DataBound(object sender, EventArgs e)
        {
            if (Session["ExpandedNodes"] is List<int> expanded)
            {
                foreach (TreeListDataItem item in RadTreeList1.Items)
                {
                    int id = (int)item.GetDataKeyValue("ID");
                    if (expanded.Contains(id))
                        item.Expanded = true;
                }
            }
        }

        protected void RadTreeList1_ItemCommand(object sender, TreeListCommandEventArgs e)
        {
            if (e.CommandName == "EditItem" && e.Item is TreeListDataItem dataItem)
            {
                int id = (int)dataItem.GetDataKeyValue("ID");
                Response.Redirect($"EditPage.aspx?id={id}");
            }
        }

       
        private DataTable GetData()
        {
            DataTable table = new DataTable();
            table.Columns.Add("ID", typeof(int));
            table.Columns.Add("ParentID", typeof(int));
            table.Columns.Add("Text", typeof(string));
            table.Columns.Add("Value", typeof(string));

            // Root nodes
            table.Rows.Add(1, DBNull.Value, "Root 1", "A");
            table.Rows.Add(2, DBNull.Value, "Root 2", "B");

            // Children of Root 1
            table.Rows.Add(3, 1, "Child 1.1", "A1");
            table.Rows.Add(4, 1, "Child 1.2", "A2");

            // Children of Root 2
            table.Rows.Add(5, 2, "Child 2.1", "B1");
            table.Rows.Add(6, 2, "Child 2.2", "B2");

            // Sub-child
            table.Rows.Add(7, 3, "SubChild 1.1.1", "A1a");

            return table;
        }
    }
}

[Leslie]

Hello,

You can restore all levels by calling Rebind() and using the correct order of operations. Restore expanded state after binding (in PreRenderComplete) and ensure parent items are expanded before children. Use recursive logic for hierarchical structures.

Here’s the adjusted code:

using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using Telerik.Web.UI;

namespace SysMgmt.Groups
{
    public partial class GroupMaintenanceServer : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            RadTreeList1.NeedDataSource += RadTreeList1_NeedDataSource;
            RadTreeList1.DataBound += RadTreeList1_DataBound;

            if (!IsPostBack)
            {
                RadTreeList1.Rebind();
            }
        }

        protected void RadTreeList1_NeedDataSource(object sender, TreeListNeedDataSourceEventArgs e)
        {
            RadTreeList1.DataSource = GetData();
        }

        // ✅ Store expanded nodes before render
        protected void Page_PreRender(object sender, EventArgs e)
        {
            var expandedItems = RadTreeList1.Items
                .Where(i => i.Expanded)
                .Select(i => (int)i.GetDataKeyValue("ID"))
                .ToList();

            Session["ExpandedNodes"] = expandedItems;
        }

        // ✅ Restore all expansions after full binding
        protected void RadTreeList1_DataBound(object sender, EventArgs e)
        {
            if (Session["ExpandedNodes"] is List<int> expanded)
            {
                foreach (TreeListDataItem item in RadTreeList1.Items)
                {
                    int id = (int)item.GetDataKeyValue("ID");
                    if (expanded.Contains(id))
                        item.Expanded = true;
                }
            }
        }

        protected void RadTreeList1_ItemCommand(object sender, TreeListCommandEventArgs e)
        {
            if (e.CommandName == "EditItem" && e.Item is TreeListDataItem dataItem)
            {
                int id = (int)dataItem.GetDataKeyValue("ID");
                Response.Redirect($"EditPage.aspx?id={id}");
            }
        }

        private DataTable GetData()
        {
            DataTable table = new DataTable();
            table.Columns.Add("ID", typeof(int));
            table.Columns.Add("ParentID", typeof(int));
            table.Columns.Add("Text", typeof(string));
            table.Columns.Add("Value", typeof(string));

            // Root nodes
            table.Rows.Add(1, DBNull.Value, "Root 1", "A");
            table.Rows.Add(2, DBNull.Value, "Root 2", "B");

            // Children of Root 1
            table.Rows.Add(3, 1, "Child 1.1", "A1");
            table.Rows.Add(4, 1, "Child 1.2", "A2");

            // Children of Root 2
            table.Rows.Add(5, 2, "Child 2.1", "B1");
            table.Rows.Add(6, 2, "Child 2.2", "B2");

            // Sub-child
            table.Rows.Add(7, 3, "SubChild 1.1.1", "A1a");

            return table;
        }
    }
}