using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;

namespace WebApplication3
{
    public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        // Обработка события разворачивания узла дерева
        protected void TreeView1_TreeNodePopulate(object sender, TreeNodeEventArgs e)
        {
            if (e.Node.ChildNodes.Count == 0)
            {
                switch (e.Node.Depth)
                {
                    case 0:
                        PopulateNames(e.Node);
                        break;
                }
            }
        }

        // Заполнение узла данными из БД
        void PopulateNames(TreeNode node)
        {
            SqlCommand sqlQuery = new SqlCommand("Select Name, Id From People");
            DataSet resultSet;
            resultSet = RunQuery(sqlQuery);
            if (resultSet.Tables.Count > 0)
            {
                foreach (DataRow row in resultSet.Tables[0].Rows)
                {
                    TreeNode NewNode = new TreeNode(row["Name"].ToString(), row["Id"].ToString());
                    NewNode.PopulateOnDemand = true;
                    NewNode.SelectAction = TreeNodeSelectAction.Select;
                    node.ChildNodes.Add(NewNode);
                }
            }
        }

        // Выполнение запроса
        private DataSet RunQuery(SqlCommand sqlQuery)
        {
            string connectionString = ConfigurationManager.ConnectionStrings["testdbConnectionString"].ConnectionString;
            SqlConnection DBConnection = new SqlConnection(connectionString);
            SqlDataAdapter dbAdapter = new SqlDataAdapter();
            dbAdapter.SelectCommand = sqlQuery;
            sqlQuery.Connection = DBConnection;
            DataSet resultsDataSet = new DataSet();
            try
            {
                dbAdapter.Fill(resultsDataSet);
            }
            catch
            {
                //labelStatus.Text = "Unable to connect to SQL Server.";
            }
            return resultsDataSet;
        }

        private void ShowMessageBox(string text)
        {
            string script = "alert(\"" + text + "\");";
            ScriptManager.RegisterStartupScript(this, GetType(), "ServerControlScript", script, true);
        }

        protected void TreeView1_SelectedNodeChanged(object sender, EventArgs e)
        {
            ShowMessageBox(TreeView1.SelectedNode.Text);
        }
    }
}