ASP.NET

public partial class MasterPage : System.Web.UI.MasterPage
{
    SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["SilverOnline"].ConnectionString);
    protected void Page_Load(object sender, EventArgs e)
    {
        populatemenu();
    }
    private void populatemenu()
    {
        //SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["Jajaipur"].ConnectionString);
        //Menu mnu = new Menu();
       
        SqlDataReader dr = null;
        string str = "Select * From Cat1";
        SqlCommand cmd = new SqlCommand(str, conn);
        conn.Open();
        dr = cmd.ExecuteReader();
        while (dr.Read())
        {
            MenuItem mt = new MenuItem();
            mt.Text = dr["CatName"].ToString();
            mt.Value = dr["Cat1ID"].ToString();
            mt.NavigateUrl = "Displaymenu.aspx?id=" + mt.Value;
            string s = mt.Value;
            conn.Close();
            string str1 = "Select * From Cat2 where(Cat1ID='" + s + "')";
            SqlCommand cmd1 = new SqlCommand(str1, conn);
            conn.Open();
            dr = cmd1.ExecuteReader();
            while (dr.Read())
            {
                MenuItem mf = new MenuItem();
                mf.Text = dr["Cat2Name"].ToString();
                mf.Value = dr["Cat2ID"].ToString();
                mf.NavigateUrl = "Displaysubmenu.aspx?id=" + mf.Value;
                mt.ChildItems.Add(mf);
                
            }
            
        }
        conn.Close();
        Menu1.Items.Add(mt);
        
        
    }
}