public static void Update <TItem>(IDataGrid grid, Func <TItem, bool> getSelected) where TItem : class, new() { var grd = grid.As <DataGrid <TItem, object> >(); var toolbar = grd.Element.Children(".s-Toolbar"); if (toolbar.Length == 0) { return; } var btn = toolbar.GetWidget <Toolbar>() .FindButton("select-all-button"); var items = grd.View.GetItems(); btn.ToggleClass("checked", items.Count > 0 && !items.Some(x => !getSelected(x))); }