public static void SetHeaderStyle( StateBag viewState, DataControlFieldCollection columns, string AscendingClassName, string DescendingClassName) { SortDirection sortDirection = SortDirection.Ascending; if (viewState[Const.SortDirection] != null) { sortDirection = (SortDirection)viewState[Const.SortDirection]; } var column = viewState[Const.SortExpression] as string; if (typeof(BoundField) == columns.GetType()) { foreach (BoundField field in columns) { if (field.DataField == column) { field.HeaderStyle.CssClass = sortDirection == SortDirection.Ascending ? AscendingClassName : DescendingClassName; } else { field.HeaderStyle.CssClass = string.Empty; } } } }