How to use Automapper to project object to Dto in LINQ

Question

I am working on .NET Core 6 along with EF Core. I want to convert Customer and Order object that I have inside LINQ select to CustomerDto and OrderDto using ProjectTo.

Using libraries

using AutoMapper;
using AutoMapper.QueryableExtensions;

I am aware how to map IQueryable using the code shown here:

var x = (from customer in db.Customers
         where customer.CustomerId == CustomerId
         select customer).ProjectTo<CustomerDto>(_mapper.ConfigurationProvider);

but I'm not sure how to project inside new or if it should be done differently? Below is LINQ code that I want customer to CustomerDto & Order to OrderDto

var customerOrdersQuery =
            (from customer in db.Customers.Where(x => x.CustomerId == CustomerId)
             join orders in db.Orders on customer.CustomerId equals orders.CustomerId into cst_Ord
             from customerOrders in cst_Ord.DefaultIfEmpty()
             select new { 
                 customer,        //ProjectTo<CustomerDto>
                 customerOrders   //ProjectTo<OrderDto>
             }).AsEnumerable();

Answer 1

Afaik you need an intermediary class CustomerWithOrdersSource which you map to CustomerWithOrdersDto, using Automapper's ProjectTo.

Mapping

public class CustomerWithOrdersSource
{
   public Customer Customer {get;set;}
   public ICollection<Order> Orders {get;set;}
}
public class CustomerWithOrdersDto
{
   public CustomerDto Customer {get;set;}
   public ICollection<OrderDto> Orders {get;set;}
}
CreateMap<CustomerWithOrdersSource, CustomerWithOrdersDto>();

Query

var customerOrdersQuery =
            (from customer in db.Customers.Where(x => x.CustomerId == CustomerId)
             join orders in db.Orders on customer.CustomerId equals orders.CustomerId into cst_Ord
             from customerOrders in cst_Ord.DefaultIfEmpty()
             select new CustomerWithOrdersSource() { 
                 Customer = customer,
                 Orders = customerOrders
             }).ProjectTo<CustomerWithOrdersDto>(_mapper.ConfigurationProvider);

Edit: According to @Lucian Bargaoanu you can project directly from anonymous object as well. But this way you could easily customize the mapping by editing the mapping profile, if necessary later on.