How to sort the gridview data ASP.Net?

protected void gvManageList_Sorting(object sender, GridViewSortEventArgs e)
        {
            try
            {
                gvManageList.EditIndex = -1; 
                string sortExpression = e.SortExpression;
                if (GridViewSortDirection == SortDirection.Ascending)
                {
                    GridViewSortDirection = SortDirection.Descending;
                    BindManageListGrid(sortExpression, " DESC ");
                }
                else
                {
                    GridViewSortDirection = SortDirection.Ascending;
                    BindManageListGrid(sortExpression, " ASC ");
                }
                
            }
            catch (Exception ex)
            {
                ex.HandleException(ExceptionLayer.UI);
                Response.Redirect("CustomError.aspx", false);
            }
        }

        private SortDirection GridViewSortDirection
        {
            get
            {
                if (ViewState["sortDirection"] == null)
                    ViewState["sortDirection"] = SortDirection.Ascending;
                return (SortDirection)ViewState["sortDirection"];
            }
            set
            {
                ViewState["sortDirection"] = value;
            }
        }

        public void BindManageListGrid(string sortby, string direction)
        {
            if (Session["ManageList"] != null)
            {
                DataTable dtList = Session["ManageList"] as DataTable;
                if (dtList.Rows.Count > 0)
                {
                    DataView dv = new DataView(dtList);
                    if (sortby.Length > 0)
                        dv.Sort = sortby + direction;
                    Session["ManageList"] = dv.ToTable();
                    gvManageList.DataSource = dv.ToTable();
                    gvManageList.DataBind();
                }
                else
                {
                    Session["ManageList"] = null;
                }
            }
           
        }