Improving Performance - Entity Framework 6 Recipes - page 472

To load all of the Customers in a given city together with their credit cards and transactions without using
Include() , explicitly load the entities and let Entity Framework fix up the associations, as shown in Listing 13-26.
Listing 13-26. Loading Related Entities without Using Include()
using (var context = new Recipe9Context())
{
var cust1 = new Customer { Name = "Robin Rosen", City = "Raytown" };
var card1 = new CreditCard { CardNumber = "41949494338899",
ExpirationDate = DateTime.Parse("12/2010"), Type = "Visa" };
var trans1 = new Transaction { Amount = 29.95M };
card1.Transactions.Add(trans1);
cust1.CreditCards.Add(card1);
var cust2 = new Customer { Name = "Bill Meyers", City = "Raytown" };
var card2 = new CreditCard { CardNumber = "41238389484448",
ExpirationDate = DateTime.Parse("12/2013"), Type = "Visa" };
var trans2 = new Transaction { Amount = 83.39M };
card2.Transactions.Add(trans2);
cust2.CreditCards.Add(card2);
context.Customers.Add(cust1);
context.Customers.Add(cust2);
context.SaveChanges();
}
using (var context = new Recipe9Context())
{
var customers = context.Customers.Where(c => c.City == "Raytown");
var creditCards = customers.SelectMany(c => c.CreditCards);
var transactions = creditCards.SelectMany(cr => cr.Transactions);
// execute queries, EF fixes up associations
customers.ToList();
creditCards.ToList();
transactions.ToList();
foreach (var customer in customers)
{
Console.WriteLine("Customer: {0} in {1}", customer.Name, customer.City);
foreach (var creditCard in customer.CreditCards)
{
Console.WriteLine("\tCard: {0} expires on {1}",
creditCard.CardNumber, creditCard.ExpirationDate.ToShortDateString());
foreach (var trans in creditCard.Transactions)
{
Console.WriteLine("\t\tTransaction: {0}", trans.Amount.ToString("C"));
}
}
}
}