Good afternoon. I have a user registration screen that works well. However I am creating a button that open a window that contains a textfield, combobox and a button. My intention in this window is to fill the combobox with the users listed in Active Directory and from the selection of a user login to fill out this user in textfield. And when I click the OK button to transfer the name, User and e-mail to the user account window.

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="ActiveDirectoryUsuario.aspx.cs"
    Inherits="Stoque.ECM.Web.Configurador.Forms.ActiveDirectoryUsuario" %>

<%@ Register Assembly="Ext.Net" Namespace="Ext.Net" TagPrefix="ext" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>    
    <%--Store UsuarioAD--%>
    <ext:Store ID="StoreUsuarioAD" runat="server">
        <Reader>
            <ext:JsonReader IDProperty="nome">
                <Fields>
                    <ext:RecordField Name="nome" />
                    <ext:RecordField Name="usuario" />
                    <ext:RecordField Name="email" />
                </Fields>
            </ext:JsonReader>
        </Reader>
    </ext:Store>
    <ext:ResourceManager ID="ResourceManagerActiveDirectoryUsuario" runat="server" Theme="Gray" />
    <form id="form1" runat="server">
    <ext:Panel ID="WindowActiveDirectory" runat="server" Height="330" Width="283" Layout="absolute"
        Frame="true">
        <Items>
            <ext:Panel ID="PanelActiveDirectoryNovo" runat="server" Height="350" Width="400"
                Layout="absolute" X="0" Y="0">
                <Items>
                    <ext:TextField ID="TextFieldLoginAD" runat="server" FieldLabel="Login" LabelWidth="60"
                        X="0" Y="0" Disabled="true" />
                        <ext:ComboBox ID="ComboBoxUsuario"
                            runat="server"
                            FieldLabel="Usuário"
                            LabelWidth="60"
                            X="0" Y="30" 
                            StoreID="StoreUsuarioAD"
                            LoadingText="Carregando ..."
                            ForceSelection="true" 
                            EmptyText="... Selecione ..."
                            DisplayField="nome" 
                            ValueField="usuario" 
                            Width="250" 
                            AutoPostBack="true"
                            >
                            <DirectEvents>
                                <Select OnEvent="ComboBoxUsuario_OnValueChanged"  >
                                    <EventMask ShowMask="true" Msg="Carregando..."/>
                                </Select>                            
                            </DirectEvents>
                        </ext:ComboBox>                   
                    <ext:Button ID="ButtonOK" runat="server" Text="OK" X="5" Y="60">
                        <DirectEvents>
                            <Click OnEvent="ButtonOK_Click" />
                        </DirectEvents>
                    </ext:Button>
                </Items>
            </ext:Panel>
        </Items>
    </ext:Panel>
    </form>
</body>
</html>
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using Ext.Net;
using Stoque.ECM.Web.Configurador.ServicoECM;
using Newtonsoft.Json;
using System.Data.Services.Client;
using Stoque.ECM.Web.Configurador.Uteis;
using Stoque.ECM.Web.Configurador.Forms;

using System.DirectoryServices.ActiveDirectory;
using System.DirectoryServices;
using System.Text;
using System.Data;

namespace Stoque.ECM.Web.Configurador.Forms
{
    public partial class ActiveDirectoryUsuario : PaginaBase
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {

            }
            CarregarStoreUsuarioAD();
            CarregarCombo();
            ComboBoxUsuario.Text = string.Empty;
        }

        # region Ações

        protected DataTable ListarUsuariosAD()
        {
            string LDAP = "";
            DataTable table = new DataTable("Resultados");

            table.Columns.Add("Nome");
            table.Columns.Add("Usuario");
            table.Columns.Add("Email");

            DataRow row = null;
            DirectoryEntry deRoot = new DirectoryEntry(LDAP);
            DirectorySearcher deSrch = new DirectorySearcher(deRoot, "(&(objectClass=user)(objectCategory=person))");

            deSrch.PropertiesToLoad.Add("cn");
            deSrch.PropertiesToLoad.Add("userPrincipalName");
            deSrch.PropertiesToLoad.Add("sAMAccountName");
            deSrch.PropertiesToLoad.Add("mail");

            deSrch.Sort.PropertyName = "sAMAccountName";

            foreach (SearchResult oRes in deSrch.FindAll())
            {
                row = table.NewRow();
                row["Nome"] = oRes.Properties["cn"][0].ToString();
                row["usuario"] = oRes.Properties["sAMAccountName"][0].ToString();

                if (oRes.Properties.Contains("mail"))
                {
                    row["Email"] = oRes.Properties["mail"][0].ToString();
                }
                table.Rows.Add(row);
            }
            return table;
        }
             
        protected void CarregarCombo()
        {
            Ext.Net.JsonReader reader = new Ext.Net.JsonReader();
            DataTable usuariosAD = ListarUsuariosAD();
            List<Ext.Net.ListItem> items = new List<Ext.Net.ListItem>();

            int i = 1;

            foreach (DataRow da in usuariosAD.Rows)
            {
                object[] array = da.ItemArray;

                if (i == 1)
                {
                    ComboBoxUsuario.SelectedItem.Value = array[0].ToString();
                }
                
                items.Add(new Ext.Net.ListItem(array[0].ToString()));

                i++;
            }

            ComboBoxUsuario.Items.AddRange(items);

            StoreUsuarioAD.DataSource = usuariosAD;
            StoreUsuarioAD.DataBind();

            this.Session["UsuariosADSistema"] = usuariosAD;
        }

        protected void MostrarDadosOutrosCampos()
        {
            if (ComboBoxUsuario.SelectedIndex > -1)
            {                
                TextFieldLoginAD.Text = ComboBoxUsuario.SelectedItem.Text;
            }
        }
        
        protected void ComboBoxUsuario_OnValueChanged(object sender, DirectEventArgs e)
        {
            MostrarDadosOutrosCampos();
            //if (ComboBoxUsuario.SelectedIndex > -1)
            //{
            //    this.Session["UsuarioAD"] = ComboBoxUsuario.SelectedItem.Value.ToString();
            //    TextFieldLoginAD.Text = ComboBoxUsuario.SelectedItem.Value.ToString();
            //}
            //return TextFieldLoginAD.Text;
        }
        
        protected void ButtonOK_Click(object sender, DirectEventArgs e)
        {

        }
        
        #endregion Ações





        #region Stores

        protected void CarregarStoreUsuarioAD() 
        {
            using (ServicoECMClient proxy = new ServicoECMClient())
            {
                this.Session["UsuariosADSistema"] = ListarUsuariosAD();
            }
            StoreUsuarioAD.DataSource = this.Session["UsuariosADSistema"];
            StoreUsuarioAD.DataBind();
        }

        #endregion Stores


    }
}