How can i add parent,child,sub child nodes on treeview in asp.net?

[basheed abdal]

In the below code was executed succesful but it doesn't added child and subnodes plse send me code how can i add child nodes and subchild nodes in treeview aswellas in to database ,pleas help me

public void treeviewcontrol()
    {
        //con.Open();
        TreeView1.Nodes.Clear();
        SqlCommand cmd=new SqlCommand("select groups from treeview",con);
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        DataSet ds = new DataSet();
        da.Fill(ds);
        con.Open();
        foreach (DataRow dr in ds.Tables[0].Rows)
        {
            TreeNode group = new TreeNode();
            group.Text = dr["groups"].ToString();
            group.Value = dr["groups"].ToString();
            //TreeView1.Nodes.Add(group);
            
            SqlCommand cmd1 = new SqlCommand("select subgroup from treeview where groups='" + group.Value+"'",con );
            SqlDataAdapter da1 = new SqlDataAdapter(cmd1);
            DataSet ds1 = new DataSet();
           
            da1.Fill(ds1);
          
            foreach (DataRow dr1 in ds1.Tables[0].Rows)
            {
                TreeNode subgroup = new TreeNode();
                subgroup.Text = dr1["subgroup"].ToString();
                subgroup.Value = dr1["subgroup"].ToString();
                group.ChildNodes.Add(subgroup);
                
                SqlCommand cmd2 = new SqlCommand("select item from treeview where groups='" + group.Value+"'",con );
                SqlDataAdapter da2 = new SqlDataAdapter(cmd2 );
                DataSet ds2 = new DataSet();
                da2.Fill(ds2);
                foreach (DataRow dr2 in ds2.Tables[0].Rows) 
                {
                    TreeNode item = new TreeNode();
                    item.Text = dr2["item"].ToString();
                    item.Value = dr2["item"].ToString();
                  subgroup.ChildNodes.Add(item );
                 item.CollapseAll();
                   
                } 
            }
            TreeView1.Nodes.Add(group);
        }
        

        con.Close();
        
        TreeView1.ExpandAll();