//get data w/ sort expression
        DataTable dt = (DataTable)gridview1.DataSource;

        //bind sorted data to another control
        chartcontrol.datasource = dt.DefaultView.ToTable();
        chartcontrol.databind();

        //add sorted ids to session to get crazy with
        if (dt != null)
        {
            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                sb.Append(dt.DefaultView[i]["ID"].ToString() + ",");
            }
            if (sb.Length > 0)
                sb.Remove(sb.Length - 1, 1);

            Session["SortedIDs"] = sb.ToString();
         }