Question

Assuming I have Customer and Order objects, where one Customer can have many Orders (so the Order class has a CustomerId property), and I want to return a collection of all CustomerAndMostRecentOrder objects which are defined as follows:

public class CustomerAndMostRecentOrder
{
  public Customer Customer { get; set; }
  public Order MostRecentOrder { get; set; }
}

How would I write a Linq query which does this (I’m using Linq to SQL)?

Answer 1

You will need to have an CreatedDate date in your Order table to get the most recent order. Then to get your CustomerAndMostRecentOrder object, do the following query:

from c in customers
join o in orders on c.ID equals o.CustomerID into co
select new CustomerAndMostRecentOrder
{
    Customer = c,
    MostRecentOrder = co.OrderByDescending(o => o.CreatedDate).FirstOrDefault()
}