Asendind and decending in Grid view

OnSortCommand="datagrid1_SortCommand" AllowSorting="true" and set SortExpression="ColumnName" for which column you want sort

public static int numberDiv;
protected void datagrid1_SortCommand(object source, DataGridSortCommandEventArgs e)
    {
        
            SqlDataReader dr = null;
            dr = objSource.GetList();
            DataSet ds = new DataSet();
            DataTable dt = new DataTable();
            dt.Load(dr);
            DataView dv = new DataView(dt);

            if ((numberDiv % 2) == 0)
                dv.Sort = e.SortExpression + " " + "ASC";
            else
                dv.Sort = e.SortExpression + " " + "DESC";
            numberDiv++;
            datagrid1.DataSource = dv;
            datagrid1.DataBind();
           
        
    }