как отсортировать всю страницу, но теперь я могу отсортировать только показ страницы

Question

Код для привязки сетки

 protected void GridView1_Sorting(object sender,GridViewSortEventArgs e)
            {
                //Retrieve the table from the session object.
                DataTable dt = Session["dtTemp"] as DataTable;

                if (dt != null)
                {
                    //Sort the data.
                    dt.DefaultView.Sort = e.SortExpression + " " + GetSortDirection(e.SortExpression);
                    GridView1.DataSource = Session["dtTemp"];
                    GridView1.DataBind();
                }
            }

код для сортировки направления на странице

private string GetSortDirection(string column)
    {
        // By default, set the sort direction to ascending.
        string sortDirection = "ASC";
        // Retrieve the last column that was sorted.
        string sortExpression = ViewState["SortExpression"] as string;
        if (sortExpression != null)
        {
            // Check if the same column is being sorted.
            // Otherwise, the default value can be returned.
            if (sortExpression == column)
            {
                string lastDirection = ViewState["SortDirection"] as string;
                if ((lastDirection != null) && (lastDirection == "ASC"))
                {
                    sortDirection = "DESC";
                }
            }
        }
        // Save new values in ViewState.
        ViewState["SortDirection"] = sortDirection;
        ViewState["SortExpression"] = column;

        return sortDirection;
    }