private void OnDriverSelectCheckedChanged(object parameter) { SelectableDriver selectableDriver = parameter as SelectableDriver; selectableDriver.IsSelected = !selectableDriver.IsSelected; if (Drivers.All(x => x.IsSelected)) { IsAllSelected = true; } else if (Drivers.Count(x => x.IsSelected) > 0) { IsAllSelected = null; } else { IsAllSelected = false; } EnableDisableReportTypeDropdown(); }