Error in DataServiceBase.OrderItems class

[fmassicci]

public async Task UpdateOrderItemAsync(OrderItem orderItem)
{
if (orderItem.OrderLine > 0)
{
_dataSource.Entry(orderItem).State = EntityState.Modified;
}
else
{
orderItem.OrderLine = _dataSource.OrderItems.Where(r => r.OrderID == orderItem.OrderID).Select(r => r.OrderLine).DefaultIfEmpty(0).Max() + 1;
// TODO:
//orderItem.CreateOn = DateTime.UtcNow;
_dataSource.Entry(orderItem).State = EntityState.Added;
}
// TODO:
//orderItem.LastModifiedOn = DateTime.UtcNow;
//orderItem.SearchTerms = orderItem.BuildSearchTerms();
return await _dataSource.SaveChangesAsync();
}

orderItem.OrderLine = .... not working

[fmassicci]

In reference to my post I would like to suggest a solution:
IList items = _dataSource.OrderItems.Where(r => r.OrderID == objItem.OrderID).ToList();
objItem.OrderLine = items.Select(r => r.OrderLine).DefaultIfEmpty(0).Max() + 1;