TreeView control in ASP.NET 2.0 with C# does not work as expected

using System;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
namespace A_MOC_DEV  
{    public partial class frm_A_Sample_Tree_02 : System.Web.UI.Page
    {        protected void Page_Load(object sender, EventArgs e)
        {        }  // protected void Page_Load(object sender, EventArgs e)
        protected void TreeView1_TreeNodePopulate(object sender, TreeNodeEventArgs e)
        {   if (e.Node.ChildNodes.Count == 0)
            {   switch (e.Node.Depth)
                {   case 0:
                        PopulateLevel2(e.Node);
                        break;
                    default:
                    // case 1:
                        PopulateLevel3(e.Node);
                        break;
                }
            }
        }  // protected void TreeView1_TreeNodePopulate(object sender, TreeNodeEventArgs e)
        void PopulateLevel2(TreeNode node2)
        {  SqlCommand scLevel2 = new SqlCommand("SELECT SO, [SOMERSET MILL] AS SAP_Func_Loc " + 
                                                " FROM tblSapFunctionalLocation " + 
                                                " WHERE (LEN(SO) = 5) ORDER BY SO");
            DataSet dsLevel2set;
            dsLevel2set = RunQuery(scLevel2);
            if (dsLevel2set.Tables.Count > 0)
            {   foreach (DataRow row in dsLevel2set.Tables[0].Rows)
                {   TreeNode NewNodeL2 = new
                    TreeNode(row["SO"].ToString(), row["SAP_Func_Loc"].ToString());
                    NewNodeL2.PopulateOnDemand = true;
                    NewNodeL2.SelectAction = TreeNodeSelectAction.Expand;
                    node2.ChildNodes.Add(NewNodeL2);
                }  // foreach (DataRow row in dsLevel2set.Tables[0].Rows)
            }  // if (dsLevel2set.Tables.Count > 0)
        }  // void PopulateLevel2(TreeNode node)
        void PopulateLevel3(TreeNode node3)
        {  SqlCommand scLevel3 = new SqlCommand();
            scLevel3.CommandText = "SELECT SO, [SOMERSET MILL] AS SAP_Func_Loc " + 
                                    " FROM tblSapFunctionalLocation " + 
                                    " where len(so)=" + (node3.Text.Length + 4).ToString() + 
                                    " and (substring(so,1," + node3.Text.Length.ToString() + ") = @parent) " +
                                    " order by so";
            scLevel3.Parameters.Add("@parent", SqlDbType.VarChar).Value = node3.Text;  
            DataSet dsLevel3set;
            dsLevel3set = RunQuery(scLevel3);
            if (dsLevel3set.Tables.Count > 0)
            {   foreach (DataRow row in dsLevel3set.Tables[0].Rows)
                {   TreeNode NewNodeL3 = new
                    TreeNode(row["SO"].ToString(), row["SAP_Func_Loc"].ToString());
                    NewNodeL3.PopulateOnDemand = true;                   // true;
                    NewNodeL3.SelectAction = TreeNodeSelectAction.Expand;           
                    node3.ChildNodes.Add(NewNodeL3);
                }  // foreach (DataRow row in dsLevel2set.Tables[0].Rows)
            }  // if (dsLevel2set.Tables.Count > 0)
        }  // void PopulateLevel3(TreeNode node)
        private DataSet RunQuery(SqlCommand scLevel)
        { string connect25 = "MOCDEV_LocalConnectionString";
            SqlConnection objConn25 = new SqlConnection();
            objConn25.ConnectionString = ConfigurationManager.ConnectionStrings[connect25].ConnectionString;
            SqlDataAdapter daLevel = new SqlDataAdapter();
            daLevel.SelectCommand = scLevel;
            scLevel.Connection = objConn25;
            DataSet LevelDataSet = new DataSet();
            try
            { daLevel.Fill(LevelDataSet);
            } // try
            catch
            {   Label1.Text = "Unable to connect to SQL Server.";
                Label1.ForeColor = System.Drawing.Color.Red;
            }  // catch
            return LevelDataSet;
        }  //  private DataSet RunQuery(SqlCommand scLevel)
    }  //public partial class frm_A_Sample_Tree_01 : System.Web.UI.Page
}  //namespace A_MOC_DEV
                                              

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//** START  OF  TREE  VIEW  CODE - executed when user starts using it *
 
    protected void TreeView1_SelectedNodeChanged(object sender, EventArgs e)
    {
        TreeNode currentNode = ((TreeView)sender).SelectedNode;
        lblSAPLoc.Text = Session["SAPFuncLoc"].ToString();
    }  // TreeView1_SelectedNodeChanged
    
    protected void TreeView1_TreeNodeCheckChanged(object sender, TreeNodeEventArgs e)
    {
        TreeNode currentNode = ((TreeView)sender).SelectedNode;
        Session["PageLifeCycle"] = Session["PageLifeCycle"] + "TreeNodeCheckChanged: " + currentNode.Text.ToString() + "; " + currentNode.Value.ToString() + "<br />";
        //            lblDebug.Text = Session["PageLifeCycle"].ToString();
    }  //  TreeNodeCheckChanged
    
    protected void TreeView1_TreeNodeExpanded(object sender, TreeNodeEventArgs e)
    {
        TreeNode currentNode = ((TreeView)sender).SelectedNode;
        if (currentNode != null)
        {
            if (currentNode.ChildNodes.Count == 0)
            {
                switch (currentNode.Depth)
                {
                    case 0:
                        PopulateLevel2(currentNode);
                        break;
                    default:
                        PopulateLevel3(currentNode);
                        break;
                }
            }
            currentNode.Expand();
        }
    }
 
    protected void TreeView1_TreeNodePopulate(object sender, TreeNodeEventArgs e)
    {
        if (IsPostBack)
        {
            TreeNode currentNode = ((TreeView)sender).SelectedNode;
            if (currentNode != null)
            {
                if (currentNode.ChildNodes.Count == 0)
                {
                    switch (currentNode.Depth)
                    {
                        case 0:
                            PopulateLevel2(currentNode);
                            break;
 
                        default:
                            PopulateLevel3(currentNode);
                            break;
                    }
                }
                currentNode.Expand();
            }
        }
        else               // when it IS NOT POSTBACK (1st time in)
        {
            int maxDepth = 1;
            if (e.Node.ChildNodes.Count == 0)
            {
                switch (e.Node.Depth)
                {
                    case 0:
                        PopulateLevel2(e.Node);
                        break;
                    default:
                        //case 1:
                        if (e.Node.Value.Length <= maxDepth)
                            PopulateLevel3(e.Node);
                        break;
                }
            }
            TreeView1.CollapseAll();
        }
 
    }  // protected void TreeView1_TreeNodePopulate(object sender, TreeNodeEventArgs e)
 
    void PopulateLevel2(TreeNode node2)
    {
        SqlCommand scLevel2 = new SqlCommand();
        scLevel2.CommandType = CommandType.StoredProcedure;
        scLevel2.CommandText = "asp_SAPLocs_node";
 
        /*          scLevel2.CommandType = CommandType.Text;
                    scLevel2.CommandText = ("SELECT Funct_Loc as SO, [TXTMD] AS SAP_Func_Loc " +
                  " FROM stg_SAP_Func_LocT WHERE (LEN(Funct_Loc) = 5) ORDER BY Funct_Loc");
         */
        scLevel2.Parameters.Add("@depth", SqlDbType.Int).Value = 5;
        scLevel2.Parameters.Add("@parent", SqlDbType.VarChar).Value = "";
        scLevel2.Parameters.Add("@site", SqlDbType.VarChar).Value = "SO";  // to be replaced by site logic
 
        DataSet dsLevel2set;
        dsLevel2set = RunQuery(scLevel2);
        if (dsLevel2set.Tables.Count > 0)
        {
            foreach (DataRow row in dsLevel2set.Tables[0].Rows)
            {
                TreeNode NewNodeL2 = new TreeNode(row["SAP_Func_Loc"].ToString(), row["SO"].ToString());
                NewNodeL2.PopulateOnDemand = true;
                NewNodeL2.SelectAction = TreeNodeSelectAction.SelectExpand;
                node2.ChildNodes.Add(NewNodeL2);
 
            }  // foreach (DataRow row in dsLevel2set.Tables[0].Rows)
        }  // if (dsLevel2set.Tables.Count > 0)
    }  // void PopulateLevel2(TreeNode node)
 
    void PopulateLevel3(TreeNode node3)
    {
        SqlCommand scLevel3 = new SqlCommand();
 
        /*          scLevel3.CommandType = CommandType.Text;
                    scLevel3.CommandText = "SELECT Funct_Loc as SO, [TXTMD] AS SAP_Func_Loc " +
                  " FROM stg_SAP_Func_LocT where len(Funct_Loc)=" + (node3.Value.Length + 4).ToString() +
                  " and (substring(Funct_Loc,1," + node3.Value.Length.ToString() + ") = @parent) order by Funct_Loc";
        */
        int NextNodeDepth = node3.Value.Length + 4;
        scLevel3.CommandType = CommandType.StoredProcedure;
        scLevel3.CommandText = "asp_SAPLocs_node";
        scLevel3.Parameters.Add("@depth", SqlDbType.Int).Value = NextNodeDepth;
        scLevel3.Parameters.Add("@parent", SqlDbType.VarChar).Value = node3.Value;
        scLevel3.Parameters.Add("@site", SqlDbType.VarChar).Value = "SO";   // to be replaced by site logic
        DataSet dsLevel3set;
        dsLevel3set = RunQuery(scLevel3);
        if (dsLevel3set.Tables.Count > 0)
        {
            foreach (DataRow row in dsLevel3set.Tables[0].Rows)
            {
                TreeNode NewNodeL3 = new TreeNode(row["SAP_Func_Loc"].ToString(), row["SO"].ToString());
                NewNodeL3.PopulateOnDemand = true;
                // NewNodeL3.Collapse();
                NewNodeL3.SelectAction = TreeNodeSelectAction.SelectExpand;
                node3.ChildNodes.Add(NewNodeL3);
            }  // foreach (DataRow row in dsLevel2set.Tables[0].Rows)
        }  // if (dsLevel2set.Tables.Count > 0)
    }  // void PopulateLevel3(TreeNode node)
 
    private DataSet RunQuery(SqlCommand scLevel)
    {
//        string connect25 = "connMOC_Dev";     //_Local_laptop";     // MOCDEV_LocalConnectionString";
        SqlConnection objConn25 = new SqlConnection();
        objConn25.ConnectionString = Session["CurrentConnectString"].ToString();   // ConfigurationManager.ConnectionStrings[connect25].ConnectionString;
        SqlDataAdapter daLevel = new SqlDataAdapter();
        daLevel.SelectCommand = scLevel;
        scLevel.Connection = objConn25;
        DataSet LevelDataSet = new DataSet();
        try
        {
            daLevel.Fill(LevelDataSet);
        } // try
        catch
        {
//            Label1.Text = "Unable to connect to SQL Server.";
//            Label1.ForeColor = System.Drawing.Color.Red;
        }  // catch
        return LevelDataSet;
 
    }  // private DataSet RunQuery(SqlCommand scLevel)
 
//  *************   END  OF  TREE VIEW CODE  ********

                                              

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