LINQ Group By and select collection

January 16, 2023 by Tarik

I think you want:

items.GroupBy(item => item.Order.Customer)
     .Select(group => new { Customer = group.Key, Items = group.ToList() })
     .ToList()

If you want to continue use the overload of GroupBy you are currently using, you can do:

items.GroupBy(item => item.Order.Customer, 
              (key, group) =>  new { Customer = key, Items = group.ToList() })
     .ToList()

…but I personally find that less clear.