I want to dynamically display submenu in asp .net
<p>I want to <code>display submenu dynamically from database</code>.But  I am getting an error in line
menuBar. <code>FindItem(dr["ParentMenuId"].ToString()).ChildItems.Add(mnu);</code> that object reference not set to an instance of an object. also I am <code>unable to display my submenu</code>. What is the error please tell me.</p>

<p>My code is:</p>

<pre><code>protected void Page_Load(object sender, EventArgs e)
{
    if (! IsPostBack)
        getMenu(); 
}

private void getMenu()
{
    SqlConnection con = new SqlConnection(@"Data Source=ST015\SQLEXPRESS;Initial Catalog=MyData;Integrated Security=True");
    con.Open();
    DataSet ds = new DataSet();
    DataTable dt = new DataTable();
    string sql = "Select * from Categories";
    SqlDataAdapter da = new SqlDataAdapter(sql, con);
    da.Fill(ds);
    dt = ds.Tables[0];
   // DataRow[] drowpar = dt.Select("ParentMenuId=" + 0);

    foreach (DataRow dr in dt.Select("ParentMenuId=" + 0))
    {
        menuBar.Items.Add(new MenuItem(dr["MenuName"].ToString(),
                dr["MenuId"].ToString(), "",
                dr["MenuDescription"].ToString()));
    }

    foreach (DataRow dr in dt.Select("ParentMenuId &gt;" + 0))
    {
        MenuItem mnu = new MenuItem(dr["MenuName"].ToString(),
                       dr["MenuId"].ToString(),
                       "", dr["MenuDescription"].ToString());
        menuBar.FindItem(dr["ParentMenuId"].ToString()).ChildItems.Add(mnu);

    }
    con.Close();
}
</code></pre>

<p>}</p>
