TreeView Disappears on PostBack

[Scott]

I have a RadTreeView on a form that is being populated by code with the node.add method described in your documentation. (http://www.telerik.com/help/aspnet-ajax/treeview-load-on-demand-client.html)  It works great for loading the items, but when you click one or do anything that causes a PostBack, all the items disappear.

APSX

<%@ Page Title="" Language="C#"  MasterPageFile="~/Content/themes/Level_One.Master" AutoEventWireup="true" CodeBehind="RequestManager.aspx.cs" Inherits="WebApplication.Forms.RequestManager" %>


<%@ Register Assembly="Telerik.Web.UI" Namespace="Telerik.Web.UI" TagPrefix="telerik" %>
<%@ MasterType VirtualPath="~/Content/themes/Level_One.Master" %>

<asp:Content ID="Content1" ContentPlaceHolderID="head" runat="server">
    <%: System.Web.Optimization.Styles.Render("~/Content/css") %>
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="main_placeholder" runat="server">
    <telerik:RadCodeBlock ID="cb1" runat="server">
        <script type="text/javascript">
            function mngRequestStarted(ajaxManager, eventArgs) {
                // alert(eventArgs.get_eventTargetElement())
                var newArr = new Array();
                for (var name in ajaxManager) {
                    newArr.push(name + "<-->" + ajaxManager[name])

                }
            }

        </script>
    </telerik:RadCodeBlock>

    <telerik:RadScriptManager ID="main_radscriptmanager" runat="server" EnableViewState="true"></telerik:RadScriptManager>
    <telerik:RadAjaxLoadingPanel ID="main_loading" runat="server" Skin="Metro" EnableViewState="true"></telerik:RadAjaxLoadingPanel>

        <telerik:RadAjaxManager ID="main_ajaxmanager" runat="server" EnableAJAX="true" EnableViewState="true" ClientEvents-OnRequestStart="mngRequestStarted">
            <AjaxSettings>
                <telerik:AjaxSetting AjaxControlID="tvRequestList">
                    <UpdatedControls>
                        <telerik:AjaxUpdatedControl ControlID="tvRequestList" LoadingPanelID="main_loading" />
                    </UpdatedControls>
                </telerik:AjaxSetting>

                <telerik:AjaxSetting AjaxControlID="main_windowmanager">
                    <UpdatedControls>
                        <telerik:AjaxUpdatedControl ControlID="main_windowmanager" LoadingPanelID="main_loading" />
                        <telerik:AjaxUpdatedControl ControlID="wndw_permissions" LoadingPanelID="main_loading" />
                    </UpdatedControls>
                </telerik:AjaxSetting>
                <telerik:AjaxSetting AjaxControlID="btnSave" EventName="Click">
                    <UpdatedControls>
                        <telerik:AjaxUpdatedControl ControlID="btnSave" UpdatePanelRenderMode="Inline" />
                    </UpdatedControls>
                </telerik:AjaxSetting>
                <telerik:AjaxSetting AjaxControlID="btnCancel"></telerik:AjaxSetting>
            </AjaxSettings>
        </telerik:RadAjaxManager>

    <asp:Button ID="cmdTest" runat="server" OnClick="cmdTest_Click" />
    <telerik:RadSplitter ID="RadSplitter1" runat="server" Height="700px" Width="100%" EnableViewState="false">
          <telerik:RadPane ID="Pane1" runat="server" Height="100%" Width="20%">
               <telerik:RadTreeView ID="tvRequestList" runat="server"
                   Skin="Metro" PersistLoadOnDemandNodes="true"
                   OnNodeExpand="tvRequestList_NodeExpand"
                   OnNodeClick="tvRequestList_NodeClick">

               </telerik:RadTreeView>
          </telerik:RadPane>
          <telerik:RadSplitBar ID="RadSplitbar1" runat="server" CollapseMode="Forward">
          </telerik:RadSplitBar>
          <telerik:RadPane ID="Pane2" runat="server">
               Pane2 - 100px
          </telerik:RadPane>
  <%--        <telerik:RadSplitBar ID="Radsplitbar2" runat="server" CollapseMode="Forward">
          </telerik:RadSplitBar>
          <telerik:RadPane ID="Pane3" runat="server" Height="150">
               Pane3 - 150px
          </telerik:RadPane>--%>
     </telerik:RadSplitter>
    <telerik:RadWindowManager runat="server" ID="RadWindowManager1" EnableViewState="true"></telerik:RadWindowManager>
</asp:Content>

Code Behind

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using Jabil.Core;
using DataEntities.Application.Context;
using DataEntities.Application.Entities;
using Telerik.Web.UI;
using System.Collections;
using System.Collections.Generic;

namespace WebApplication.Forms
{
    public partial class RequestManager : FrameworkPage
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            this.Master.PageTitle = "Request Manager";

            if (!IsPostBack)
            {
                LoadRootNodes(tvRequestList);
            }
        }

        private void LoadRootNodes(RadTreeView tv)
        {
            using (RequestsDataContext rdc = new RequestsDataContext(string.Empty))
            {
                List<RequestManagerTreeList> tl = rdc.GetRequestManagerTreeViewList(1, 0, false).ToList<RequestManagerTreeList>();
                foreach (RequestManagerTreeList tlItem in tl)
                {
                    RadTreeNode tn = new RadTreeNode();
                    tn.Text = tlItem.ItemName;
                    tn.Value = ("L1" + tlItem.ItemId.ToString());
                    tn.ExpandMode = TreeNodeExpandMode.ServerSideCallBack;
                    tv.Nodes.Add(tn);
                }
            }
        }

        protected void tvRequestList_NodeExpand(object sender, RadTreeNodeEventArgs e)
        {
            try
            {
                using (RequestsDataContext rdc = new RequestsDataContext(string.Empty))
                {
                    string itemValue = e.Node.Value;

                    if (itemValue.Substring(0, 1) == "L")
                    {
                        int level = Convert.ToInt32(itemValue.Substring(1, 1)) + 1;
                        int itemId = Convert.ToInt32(itemValue.Substring(2, itemValue.Length - 2).ToString());
                        string levelTag = "L" + level.ToString();
                        List<RequestManagerTreeList> tl = rdc.GetRequestManagerTreeViewList(level, itemId, false).ToList<RequestManagerTreeList>();
                        foreach (RequestManagerTreeList tlItem in tl)
                        {
                            RadTreeNode tn = new RadTreeNode();
                            tn.Text = tlItem.ItemName;
                            tn.Value = levelTag + tlItem.ItemId.ToString();
                            if (level < 3)
                            {
                                tn.ExpandMode = TreeNodeExpandMode.ServerSideCallBack;
                            }
                            e.Node.Nodes.Add(tn);

                        }
                    }
                }
            }
            catch (Exception ex)
            {
                LogError(ex);
                show_error_message(ex.Message);
            }
        }

        protected void tvRequestList_NodeClick(object sender, RadTreeNodeEventArgs e)
        {
            show_error_message("Test");
        }

        private void show_error_message(string error_message)
        {

            string error = error_message.Replace("'", "");


            main_ajaxmanager.ResponseScripts.Add(string.Format("window.radalert(\"" + error + "\")"));

        }

        protected void cmdTest_Click(object sender, EventArgs e)
        {
            show_error_message("Test");
        }
    }
}

[Scott]

After doing a lot of playing with this, I discovered there was an option being set on the RadSplitter that said EnableViewState="false".  After removing that, it worked fine.