Question

I’m trying to group orders by customer id then project the orders returned (by customer) into a List. Trying to figure out how I would do this?

 List<OrderGroup> set = OrderRepository.GetAllOrders
     .GroupBy(x => x.CustomerId).Select(result => new OrderGroup
         {
             Orders = ???? //should be all orders from one customer.
         }).ToList();

Answer 1

The result is an IGrouping<TKey, T>, which is itself an IEnumerable<T>, so you can do:

List<OrderGroup> set = OrderRepository.GetAllOrders
                      .GroupBy(x => x.CustomerId)
                      .Select(result => new OrderGroup
                      {
                          Orders = result.ToList()
                      }).ToList();

(Note that this assumes Orders is assignable from a List<Order>.)