C#のtreeviewバインドデータベース(再帰アルゴリズム)

最近面接の私に2つのテーマをあげて、1つはIQテストで、2つ目はテーマの言うことです
合計2つのテーブルdepartment(id int not null primary key,parentid int,name char(50);
               employee(id int not null foreign key(id)  references department(id) ,departmentid,name char(50));
実装されたコード記録は以下の通りである.

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

public partial class Default01 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        fill_Tree();

    }

    void fill_Tree()
    {
     

        SqlConnection SqlCon = new SqlConnection("server=(local);uid=sa;pwd=sa;database=test");
        SqlCon.Open();
        SqlCommand SqlCmd = new SqlCommand("Select id,name from department", SqlCon);
        SqlDataReader Sdr = SqlCmd.ExecuteReader();
        SqlCmd.Dispose();
        string[,] ParentNode = new string[10000, 2];

        int count = 0;

        while (Sdr.Read())
        {

          
            ParentNode[count, 0] = Sdr.GetValue(Sdr.GetOrdinal("id")).ToString();
            ParentNode[count++, 1] = Sdr.GetValue(Sdr.GetOrdinal("name")).ToString();

        }

        Sdr.Close();

        for (int loop = 0; loop < count; loop++)
        {
            TreeNode root = new TreeNode();
            root.Text = ParentNode[loop, 1];
            root.Target = "_blank";
            root.NavigateUrl = "Default01.aspx";

            SqlCommand Module_SqlCmd = new SqlCommand("Select name,id from employee where departmentid =" + ParentNode[loop, 0], SqlCon);

            SqlDataReader Module_Sdr = Module_SqlCmd.ExecuteReader();

            while (Module_Sdr.Read())
            {

                TreeNode child = new TreeNode();

                child.Text = Module_Sdr.GetValue(Module_Sdr.GetOrdinal("name")).ToString();

                child.Target = "_blank";

                child.NavigateUrl = "Default01.aspx";

                root.ChildNodes.Add(child);

            }

            Module_Sdr.Close();

            TreeView1.Nodes.Add(root);

        }

        TreeView1.CollapseAll();
        SqlCon.Close();

    }

    protected void TreeView1_SelectedNodeChanged(object sender, EventArgs e)
    {

    }
}