Basically I have 2 panels in my aspx file "Productos.aspx", one called "panelizq" on the left with a treepanel and one called "panelarticulos" on the right where I would like to load my "Viewportartículos.aspx" page when I click on the tree panel.

The thing is that I can only load "Viewportartículos.aspx" on "panelarticulos" in the pageload. When i try to do it by clicking on the tree, nothing happens.

Productos.aspx:

<%@ Page Title="Extranet Jhayber" Language="C#"  CodeBehind="Productos.aspx.cs" Inherits="TestB2BDeporte.Productos" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<%@ Register Assembly="Ext.Net" Namespace="Ext.Net" TagPrefix="ext" %>

<html xmlns="http://www.w3.org/1999/xhtml">
<head id="CalzadoExtranet" runat="server"></head>
<body>
    <form id="formGeneral" runat="server">
    <ext:ResourceManager ID="ResourceManagerExt" runat="server" IDMode="Explicit"  AjaxTimeout="180000"/>
    <ext:Viewport ID="Viewport1" runat="server" Layout="columnlayout" cls="backgroundcls" Frame="true">
        <Items>
            <ext:Panel ID="panelizq" runat="Server" Width="240" Frame="false" Layout="ColumnLayout" AutoScroll="false" cls="Menutabs" Scrollable="Vertical">
                <Items>
                    <ext:Label runat="server" id="Filas" Text="" Hidden="true"></ext:Label>
                    <ext:Label runat="server" id="Paginas" Text="" Hidden="true"></ext:Label>
                    <ext:Label runat="server" id="logintext" Text="" Hidden="true"></ext:Label>
                    <ext:Label runat="server" id="clientetext" Text="" Hidden="true"></ext:Label>
                    <ext:Label runat="server" id="paginaactualtext" Text="" Hidden="true"></ext:Label>
                    <ext:Label runat="server" id="filtrotext" Text="" Hidden="true"></ext:Label>

                    <ext:formPanel runat="server" Cls="Buscador" ColumnWidth="1" Layout="ColumnLayout" MarginSpec="30 0 30 0">
                        <KeyMap>
                            <ext:KeyBindItem Key="ENTER" Handler="App.direct.Filtrar();" />
                        </KeyMap>
                        <Items>                          
                            <ext:TextField runat="server" ID="buscatext" MarginSpec="7 0 0 15" Width="203" Cls="buscador"  ColumnWidth="0.85">
                                <RightButtons>
                                    <ext:Button runat="server" Icon="Magnifier" ID ="lupa">
                                        <DirectEvents>
                                            <Click DisableControl="true" OnEvent="Filtrar"></Click>
                                        </DirectEvents>
                                    </ext:Button>
                                </RightButtons>
                            </ext:TextField>

                        </Items>
                    </ext:formPanel>
                            
                </Items>
            </ext:Panel>

            <ext:Panel ID="panelarticulos" runat="Server" ColumnWidth="1" height="800" Frame="false" autoscroll="true" Cls="panelarticuloscls">
                <Loader runat="server" Mode="Frame">
                    <LoadMask ShowMask="true" MsgCls="loader" Msg="Cargando"/>
                </Loader>
            </ext:Panel>
        </Items>
    </ext:Viewport>

   </form>

</body>
</html>
Productos.aspx.cs:

Here I make the first load, that is working and I create the treepanel (this works nice)

protected void Page_Load(object sender, EventArgs e)
        {

           

            if (!IsPostBack)
            {
                panelarticulos.Loader.Url = "ViewportArticulos.aspx?login=" + logintext.Text;
                panelarticulos.LoadContent();


            }


            // CREO LOS Buttons
            int x = 0;
            int z = 0;
            int i = 0;

            
            var treeStore = new TreeStore();
            Toolbar toolBar = new Toolbar();

            Ext.Net.TreePanel tree = new Ext.Net.TreePanel();
            tree.RootVisible = false;
            tree.ID = "TreePanel1";
            tree.AutoScroll = true;

            Ext.Net.Node root = new Ext.Net.Node()
            {
                Text = "Catálogo",
                 
            };
            root.Expanded = true;
  
            CategoriaDao Cat = new CategoriaDao();
            List<Categoria> Categorias = Cat.getAll();
            int cat = 0;
            foreach (Categoria categoria in Categorias)
            {
                cat++;
                FamiliaDao Fam = new FamiliaDao();
                List<string> Sexos = Fam.GetDistinctSexos(categoria.Id);
                if(Sexos.Count > 0)
                {
                    Ext.Net.Node CatNode = new Ext.Net.Node()
                    {
                        NodeID = categoria.Id.ToString(),
                        Text = (categoria.Nombre.Substring(0, 1).ToUpper() + categoria.Nombre.Substring(1).ToLower()).Trim(),
                    };
                    root.Children.Add(CatNode);


                    foreach (string S in Sexos)
                    {
                        List<string> Familias = Fam.GetFamiliaByCategoriaYSexo(categoria.Id, S);
                        if (Familias.Count > 0)
                        {

                            Ext.Net.Node SexNode = new Ext.Net.Node()
                            {
                                NodeID = categoria.Id.ToString() + "/%"+S.Trim()+ "%",
                                Text = (S.Substring(0, 1).ToUpper() + S.Substring(1).ToLower()).Trim(),
                            };
                            CatNode.Children.Add(SexNode);
                            foreach (string familia in Familias)
                            {
                                Ext.Net.Node FamNode = new Ext.Net.Node()
                                {

                                    NodeID = categoria.Id.ToString() + "/%" + S.Trim() + "%/%" + familia.Trim()+"%",
                                    Text = (familia.Substring(0, 1).ToUpper() + familia.Substring(1).ToLower()).Trim(),

                                    Leaf = true
                                };

                                SexNode.Children.Add(FamNode);
                            }

                        }

                    }
                }
                
            }

            root.Expanded = true;
            treeStore.Root.Add(root);
            tree.Store.Add(treeStore);
            tree.ColumnWidth = 1;
            tree.Frame = false;
            tree.Cls = "clstree";

            tree.Listeners.ItemClick.Handler = "App.direct.Filtrado(record.data.id);";
          
            panelizq.Add(tree);

           

        }
And here is where the event that fires when the tree panel is clicked and where the loader fails and does nothing.
[DirectMethod]
        public void Filtrado(string Id)
        {
            
            string argumentos = "";
            string [] separadas;

            separadas = Id.Split('/');

            switch(separadas.Count())
            {
                case 1:
                    argumentos = "where categoria = " + separadas[0];
                    break;

                case 2:
                    argumentos = "where categoria = " + separadas[0] + " and Sexo like '" + separadas[1] + "'";
                    break;

                case 3:
                    argumentos = "where categoria = " + separadas[0] + " and Sexo like '" + separadas[1] + "' and familia like '" + separadas[2] + "'";
                    break;
            }

            argumentos = argumentos.Replace("'", "/-/");
            SessionVariablesDao SSD = new SessionVariablesDao();
            SSD.UpdateTo2(Convert.ToInt32(logintext.Text), "-1", "-1", "-1", argumentos, "-1", "-1", "-1", -1, -1, -1, DateTime.Now, -1);

            //THIS IS NOT WORKING//
            panelarticulos.Loader.Url = "ViewportArticulos.aspx?login=" + logintext.Text;
            this.panelarticulos.LoadContent();
           ////

        }