Recursive TreeView in ASP.NET

Question

I have an object of type list from which I wish to use to populate a treeview in asp.net c#.

Each object item has:

id | Name | ParentId

Answer 1

    //In load for example
    if (!IsPostBack)
    {
            DataSet ds = new DataSet();
            ds = getRoles(); //function that gets data collection from db.

            tvRoles.Nodes.Clear();

            BindTree(ds, null); 
            tvRoles.DataBind();

    }       

    private void BindTree(DataSet ds, TreeNode parentNode)
    {
        DataRow[] ChildRows;
        if (parentNode == null)
        {
            string strExpr = "ParentId=0";
            ChildRows = ds.Tables[0].Select(strExpr);                    
        }
        else
        {
            string strExpr = "ParentId=" + parentNode.Value.ToString();
            ChildRows = ds.Tables[0].Select(strExpr); 
        }   
        foreach (DataRow dr in ChildRows)
        {
            TreeNode newNode = new TreeNode(dr["Name"].ToString(), dr["Id"].ToString());
            if (parentNode == null)
            {
                tvRoles.Nodes.Add(newNode);
            }
            else
            {
                parentNode.ChildNodes.Add(newNode);
            }
            BindTree(ds, newNode);
        }
    }